Americans can increasingly get basic medical care in the same place they buy toothpaste and light bulbs.

In a development that has broad implications for the nation's primary-care system, a rising number of major pharmacy and retail chains -- including CVS Corp., Wal-Mart Stores Inc. and Target Corp. -- are opening in-store health clinics. They offer patients fast access to routine medical services such as strep-throat tests, sports physicals and flu shots. The clinics, which typically charge between $25 and $60 per visit, don't require an appointment and are open during pharmacy hours including evenings and weekends. To keep costs down, they are staffed by nurse practitioners, who can legally treat patients and write prescriptions in most states.

The trend is rapidly spreading in pharmacy chains as they look for ways to stem losses to mail-order pharmacies and big-box stores. Three of the nation's largest drugstore chains -- Rite Aid Corp., Brooks Eckerd Pharmacy and Osco Drug -- have announced plans to open health clinics in the coming months. All three have partnered with a Pennsylvania-based health-care start-up called Take Care Health Systems LLC that will lease space inside the pharmacies and operate the clinics.

Take Care is also in talks with Walgreen Co., the nation's largest pharmacy chain (by sales volume). The first Take Care clinics will open at Rite Aid stores in Portland, Ore., later this month; Take Care aims to have 1,300 clinics open by the end of 2007.

Other major chains have been testing the in-store clinics. CVS and Target are working with Minneapolis-based MinuteClinic to open clinics at stores in markets including Minneapolis, Baltimore and Nashville. Wal-Mart is working with InterFit Health and other companies to open clinics in Oklahoma, Arkansas, Florida and other states. (The pharmacy chains must partner with outside companies because federal health-care laws banning "self referrals" prohibit pharmacy chains from running their own clinics.)

The new clinics are aimed at everyone from harried parents dropping by with sick kids on the weekend, to busy professionals ducking in for a prescription during work hours. While the retailers don't profit directly from the new services, the hope is that the clinics will boost business if patients fill their prescription at the store pharmacy, or pick up other items on their way out. (Target's MinuteClinics even offer patients a clip-on beeper after they sign in, to encourage patients to shop until the nurse practitioner is ready to see them.)

The trend is drawing criticism from some doctors groups, who could lose business if patients turn to the clinics for basic care. Doctors also contend that patients could wind up with lower-quality care because the clinics don't have physicians on-site.

"Serious illnesses sometimes present with simple symptoms," says Edward Hill, president of the American Medical Association. "A cough might be something as simple as a cold, or something as serious as congestive heart failure. The ability to ferret out the 20 percent of serious illnesses that present with simple symptoms is what we went to medical school for."

But some patients are more concerned about convenience. When Terri Whitesel, 56 years old, who runs a marketing consultancy in Minneapolis, had an allergic reaction to a bug bite last month, she dashed into a MinuteClinic at a Target in between meetings at work. "I didn't want to go to the doctor and sit around waiting with a bunch of people who are really sick," says Ms. Whitesel.

The nurse practitioner was busy with another patient, but Ms. Whitesel wrote down her name, got a beeper at the check-in counter, and shopped for birthday cards until the nurse beeped her five minutes later. The entire visit took less than 15 minutes and she wound up with a prescription for an anti-inflammatory drug.

Both MinuteClinic and Take Care work with a network of local physicians who are available by phone if the nurse practitioner needs help with a diagnosis. And the companies say the clinics can act as an entryway to the primary-care system because they offer referrals to patients who don't have a doctor.

The companies limit their services to a strict list of roughly 30 basic services and diagnoses, ranging from athlete's foot to tetanus shots. Neither company allows nurse practitioners to prescribe drugs for health situations that require continuing care such as antidepressants, birth control or heart medications.

Health insurers have embraced the concept because the clinics promise considerable savings. While a typical doctor visit for a basic illness costs an insurer about $110, a visit to one of the clinics usually costs under $60. In addition, the clinic services are far cheaper than the emergency room, which is where patients often wind up when they need medical care outside business hours. (A strep throat test at the emergency room can cost over $300.)

Some insurers are actively encouraging patients to use the clinics by lowering the co-pay. In Minnesota, companies including Blue Cross Blue Shield of Minnesota and Graco Inc., have reduced or eliminated co-pays for employees who opt to use a MinuteClinic instead of a doctor. Take Care has deals in place with several insurers in Portland.

Chain drugstores have been grappling with relatively flat sales for the past few years. While pharmacies have broadened their offerings over the past couple of decades, and now offer everything from photo developing to outdoor grills, prescription-drug sales still account for about 68 percent of their business. To hold onto that business, pharmacies are increasingly trying to establish themselves as wellness centers that offer a constellation of health-care services related to prescriptions.

The management teams behind both of the leading companies in the field -- Take Care and MinuteClinic -- have experience in other consumer-focused industries. MinuteClinic's new chief executive officer, Michael C. Howe, is the former president and CEO of the Arby's fast-food chain, and previously worked for KFC. Hal Rosenbluth, chairman of the board of Take Care, is the former CEO of Rosenbluth International, a travel company acquired by American Express Co. in 2003 in a deal valued at over $300 million.

Take Care's business model has been influenced by Mr. Rosenbluth's background in the the travel industry, and the clinic model relies heavily on technology to increase the efficiency of care. When patients arrive, they check themselves in at a touch-screen computer terminal -- much like an airline self-check-in kiosk -- where they can swipe a credit card and enter basic information about their symptoms and family history.

In one of the more-novel uses of technology employed by Take Care, a computer software program will be involved in actually diagnosing illnesses. The patient's sign-in information will be transmitted electronically to a computer terminal inside the treatment room, where the nurse can enter additional information about the patient's symptoms and conditions as he or she talks with the patient.

The software system will eventually generate a diagnosis and a recommended course of treatment. If the nurse practitioner disagrees with a computer-generated diagnosis, he or she can opt to override the system. When a prescription is written, it will be transmitted electronically to the store pharmacy, or another pharmacy. The system will also create an electronic medical record for each patient that can be transferred to a primary-care physician.