The trouble started even before the trip.

Earlier this year, Baltimore businessman John Seed began planning a kid-free vacation to Europe with his wife. When friends hinted they'd love to come, Mr. Seed invited them along.

That's when it stopped being Mr. Seed's trip to plan. The couples wrangled over hotels for weeks -- spending three hours one night on the phone going through the options on the Internet, because the Seeds refused to stay at a place with shared bathrooms. Searching for plane tickets, Mr. Seed would find an affordable flight and call his friends, only to get their voicemail. "It's been a long and tedious process," he says.

The "friend-trip," in which people join up with friends, relatives or other families, can be a memorable way to bond and cut vacation expenses at the same time. It's a niche the travel industry is increasingly targeting, especially with hotel and other vacation costs up sharply this summer. Multifamily trips are "a big part of our market now," says a spokeswoman for Jekyll Island Club Hotel in Jekyll Island, Ga., which recently spent $5.5 million renovating two cottages, one with 10 rooms and one with 13, that groups can book in part or whole.

At Paradise Point Resort & Spa in San Diego, with several two-unit bungalows and buildings, small groups now account for about 25 percent of its summer business. Kiawah Island Golf Resort in Kiawah Island, S.C., has two small-group specialists, who often plan golf, fishing and biking outings. The hotel added a family-reunion specialist in the past year.

Eight out of 10 Americans will take at least one trip this year with friends or relatives, up by more than a third since 2001, according to a survey by travel consultants Yesawich, Pepperdine, Brown & Russell, which calls the trend "togethering." "People want to reconnect by spending more time with friends and family," says Gary Sain, the company's chief marketing officer.

With Americans so overscheduled, the time to do that is increasingly on vacation. It's particularly true for families. "Everyone is working more," says Lisa Spiegel, director of Soho Parenting in New York. "When parents get vacation time they want to spend it with their kids and their friends." Marla Schaffer, president of Great Neck, N.Y.-based Leaders in Travel, says about 70 percent of the company's 4,000 active clients now take trips with people outside their own family. She says she is booking more multifamily trips, as parents want their kids to entertain each other.

But the resulting togetherness can be painful itself, as fellow travelers bicker over everything from how much to spend on dinner to whether they should spend their time power shopping or visiting museums. Jim and JoEllen Feltham typically stay at four-star hotels, but when a friend organized a week of rafting down the Colorado River with seven other families, they signed on. They figured that at $8,000 per family, the guided trip would give their two kids a comfortable outdoor experience. At their friend's recommendation, they left behind their warm clothes and rain jackets. "We brought almost nothing based on her account," says Ms. Feltham.

The wind picked up the first afternoon, rain followed and they awoke the next morning drenched and freezing. After several days of howling storms, the Felthams, who live in Phoenix, asked if they could escape by helicopter. Their organizer-friend laughed. It all came to a head when Ms. Feltham accused the friend of using her portable shower, which was filled with bottled water. "I stormed off and didn't talk to her for the rest of the evening," says Ms. Feltham. "I'm polite and gracious, but I just wanted to wring her neck." At the end of the trip, the Felthams drove off without saying goodbye and then skipped a party several weekends later when the families all shared photos.

The vacation was put together by Lynn Hayes, who organizes family trips at familytravel.com for a living. (She and Ms. Feltham finally spoke again six weeks later, when they bumped into each other at their kids' school.) Ms. Hayes says she had not expected any storms, nor did she think it was a big deal. But she has since compiled a list of advice for clients who plan to travel with others. Among her tips: assess the compatibility of the group ahead of time by getting together for an afternoon outing and work out privacy and space concerns, so people feel they can go off on their own without offending everyone.

Travel experts say that money is often the biggest source of tension for co-travelers and that the best way to avoid problems is to deal with them upfront. Discuss how to split dinner -- person by person or item by item; find out how much everyone is comfortable spending on lodging early in the process; and hold a meeting midtrip to talk over any issues. The most important thing to remember: Go with low expectations.

That may seem like a strange starting point for an event that's supposed to be relaxing and fun. But group-behavior experts say people relate to each other best when they're getting something done together. On vacation, when they're not on their routines, they can create conflict to fill the void. "The relationship can momentarily lose its purpose," says David Sloan Wilson, professor of biology and anthropology at Binghamton University in Binghamton, N.Y. As a result, travelers can be jumpy and argumentative.

Nadine Nardi Davidson, author of "Travel With Others Without Wishing They'd Stayed Home," says that sharing a vacation only works when everyone feels they have enough space. She divides travelers into nine types, including the "relaxer," the "comfort seeker," the "culturist" and the "adventurer." The trick is learning how to negotiate with people with different styles.

This past May, Marcus Rohlfs had a hard time negotiating when he spent a week in the Napa, Calif., region with his wife, her siblings and their spouses. The plan was to meet in the early afternoon at the Rohlfs's house in Tacoma, Wash., and drive down together in one large van. Mr. Rohlfs took a half day off from work as an insurance marketing manager and waited for the others.

Four hours later, the rest of the party still had not arrived. "I thought my husband was going to have a heart attack," says his wife, Melissa Rohlfs. When the others finally got there, they wanted to do some shopping and get dinner -- and didn't set off until 10 p.m. Frequent bathroom stops for the five toddlers on board stretched the drive into a 30-hour marathon.

Punctuality became a common theme, with the stress escalating when some family members were an hour late for a $4,000 set meal at the restaurant French Laundry. When Mrs. Rohlfs's brother showed up wearing shorts, the group waited in the garden, sipping kir royals and Champagne, while Mrs. Rohlfs's sister-in-law rushed back to their rental house to fetch trousers for her husband.

Seattle software consultant Kevin Harris -- the brother who forgot his trousers -- says part of the challenge throughout the trip was balancing his family's schedule with that of Mr. and Mrs. Rohlfs, who don't have children. "When you have kids you're more relaxed about time," he says, adding that the conflict put him "on edge." The trip turned out to be fun, but next time, Mr. Rohlfs says, they'll choose their own hotel and transportation, and take some time apart from the others. "You really need time alone."

Despite the perils, many people have traveled with friends and family and had memorable bonding experiences. This summer, doubling up can look even more attractive as travel costs continue to rise. Average air fares are up 11.1 percent in 2006 from 2005, according to the Air Transport Association. Prices of regular gas are up nearly 30 percent to almost $3 a gallon since last summer, and the Travel Industry Association of America says the higher prices this summer will add $30 to $50 to the fuel bill for a typical road trip. And PricewaterhouseCoopers's hospitality-and-leisure practice predicts that room rates at high-end resorts will rise as much as 15 percent this summer. Total expenditures on travel in the U.S. increased 7.9 percent in 2005 and are expected to rise another 4.5 percent this year, says the TIA.

That's partly why Maureen Bissing was grateful when she received a dream invitation from old friends -- a free week in a 2,500-square-foot, three-bedroom open-air estate in Maui, Hawaii, with a swimming pool and a cliffside view of crashing waves. Her friends had paid $4,500 for the week at a charity auction, then invited Ms. Bissing and another couple along. As she believed good manners dictated, Ms. Bissing planned to spend time with her friends and pay for extras like food and household supplies.

The other two invitees took a different approach: The first morning they left the house at 6 a.m. and didn't return for hours. When Ms. Bissing and her friends planned a dinner of grilled fish and pineapple, the second couple offered to pay for the pineapple, which cost 50 cents. "By the end, it was all really bad," says the marketing manager from Irving, Texas. She says that after three days her friends, Rebecca and Evan Roberts, were so upset they could barely eat with the others. "We definitely needed to take a break when we got home," says Ms. Roberts, an advertising executive in Portland, Ore.

The other guests say they had no idea anything was amiss. They'd already split the cost of groceries for the house the day they arrived, though they don't eat meat or drink hard alcohol and there was plenty of both in the cart. And they'd disappeared early in the morning because they wanted to snorkel with dolphins.

As for Mr. Seed, who returned this week from the Netherlands and Belgium, he reports his trip went surprisingly well -- though it was marked by minor tension, mostly over whether to go shopping or to museums. The couples ended up agreeing to spend some of their time apart, doing different activities.

"I didn't think it was that bad," says Eileen Schurter, a special-education assistant who lives outside Baltimore and who traveled with the Seeds. She does say it was frustrating trying to coordinate the trip. A husband and wife, she notes, can feel stress traveling together, so more people can mean more challenges. But she says she was thrilled to be invited. "My favorite part of the trip was their companionship," she says. "At the end they said, 'We should do it again -- but not next year.'"

'Togethering' Spots

The travel industry is increasingly reaching out to small groups, whether it's a couple of couples or several families traveling together. Here is a sampling of resorts that are making the effort:

RESORT/LOCATION: Asilomar, Pacific Grove, Calif.
WEB SITE: http://visitasilomar.com
DAILY RATES: $121-$277
TOGETHERNESS TACTIC: "Living rooms"
COMMENTS: This resort on a beach in a state park has 28 lodges. A small group can use "living rooms" (with couches, fireplace and piano) free; but there's only one per lodge. Rates include breakfast; family-style dinners at the restaurant's large round tables with lazy Susans (for 6, 8 or 10 people) cost $16 extra. Bring books: no TVs or phones in rooms.

RESORT/LOCATION: Jekyll Island Club Hotel, Jekyll Island, Ga.
WEB SITE: jekyllclub.com
DAILY RATES: $129-$3,967
TOGETHERNESS TACTIC: Fishing outings
COMMENTS: This National Historic Landmark recently spent $5.5 million renovating two cottages that small groups can take over. Sports like bicycle scavenger hunts and dolphin watching are big, but the main attraction is the lawn: A croquet club practices there, and guests can rent such equipment as cast iron, oven-fired wickets and premium Jacques eclipse balls.

RESORT/LOCATION: Kiawah Island Golf Resort, Kiawah Island, S.C.
WEB SITE: kiawahgolf.com
DAILY RATES: $149-$5,000
TOGETHERNESS TACTIC: Small group specialists
COMMENTS: A three-bedroom house on this 10-mile private beach resort goes for as little as $300 a night in the low season; a four-bedroom villa in the high season is $620 a night. There are two "small group specialists" here who will arrange group golf and tennis lessons or kayaking or fishing trips -- but that's generally only for groups of 10 people or more.

RESORT/LOCATION: Napili Kai, Lahaina, Hawaii
WEB SITE: napilikai.com
DAILY RATES: $210-$930
TOGETHERNESS TACTIC: Photography sessions
COMMENTS: On one of the least crowded coasts of Maui, near the Ritz-Carlton in Kapalua, this condo-unit resort has a free weekly Mai Tai party and groups of eight or more get T-shirts and a free hour-long sitting with a professional photographer. The sitting is free ... but the soft-hearted might feel obligated to buy the pictures.

RESORT/LOCATION: Paradise Point, San Diego
WEB SITE: http://paradisepoint.com
DAILY RATES: $159-$5,000
TOGETHERNESS TACTIC: Two-unit bungalows
COMMENTS: An upscale (read: pricey) family-reunion spot on a private, 44-acre island where small groups account for about 25 percent of the summer business. It's possible to take over one of the two-unit bungalows or get two two-unit buildings next to each other.

RESORT/LOCATION: White Point Beach Resort, Nova Scotia, Canada
WEB SITE: whitepoint.com
DAILY RATES: $105-$500
TOGETHERNESS TACTIC: Group surf lessons
COMMENTS: There's a wide range of cottages and houses; the three-bedroom "housekeeping cottages" come with kitchen and dining areas. The resort will arrange surf lessons, mussel bakes and marshmallow roastings for small groups. But if you have kids, beware the adults: The resort had to build bleachers several years ago around its main bonfire to prevent grownups from elbowing the kids and their marshmallows away from the fire.