It's not the time involved but the pleasures imparted. And all those claims that a satisfactory sexual experience must last hours -- or all night long -- involve more bragging than reality.

A Penn State University study concludes that satisfactory sexual intercourse for couples typically lasts only three to 13 minutes, which counters the robust claims that satisfactory sex requires more time.

In their study, Eric Corty and Jenay Guardiana, researchers at Penn State Erie, The Behrend College, surveyed 50 members of the Society for Sex Therapy and Research who've collectively seen thousands of patients over several decades. About two-thirds of them responded to the survey and rated a range of time lengths for sexual intercourse -- from penetration to ejaculation -- under the categories of "adequate," "desirable," "too short" or "too long."

The group agreed one to two minutes was too short, but adequate time was three to seven minutes, with the most desirable length of time for intercourse being seven to 13 minutes. Ten to 30 minutes was too long.

Dr. Corty said the conclusions may seem surprising, given widely held beliefs, influenced by popular culture, that a satisfactory sexual experience is based on penis size, erections and all-night intercourse. Past research also found that a large percentage of men and women preferred sexual intercourse that lasted 30 minutes or longer.

"This seems to be a situation ripe for disappointment and dissatisfaction," said Dr. Corty, an associate professor of psychology. "With this survey, we hope to dispel such fantasies and encourage men and women with realistic data about acceptable sexual intercourse, thus preventing sexual disappointments and dysfunctions."

The study will be published in the May issue of the Journal of Sexual Medicine, which currently has the article, subtitled "How Long Should Intercourse Last?" published online. It states that the average sex therapist believes sexual intercourse that lasts three to 13 minutes is normal and not of clinical concern.

The results, the study continues, should help to change expectations and "prevent distress" among those who feel they're not involved in sexual activity long enough before climax.

"These results may also be beneficial to couples in treatment for sexual problems by normalizing expectations," Dr. Corty said.

But James D. Adelman, of Pine, a sex therapist with Tri-County Counseling Associates, said three to 13 minutes doesn't sound like adequate time, based on his practice.

"A short couple of minutes probably is described as a quickie because the movement toward more mutual satisfactory sexual experience involves spending more time with one's sexual partner," said Dr. Adelman, who was trained by pioneering sex researchers William Masters and Virginia Johnson. "People with sexual dysfunctions I counsel to spend 10 to 30 minutes in pleasuring each other."

Dr. Corty said he understands the study will bring some dissent. But he said his goal was to test the myth that sexual intercourse should last a long time. Previous studies involving 1,600 people, he said, already had shown that the average time span for intercourse was only five to seven minutes.

"But most people aren't aware of that, and I was curious about what sex therapists thought was normal," he said. "It was a simple idea to get a bunch of therapists and ask them."

Trying to live up to the ideal of having sex all night long is akin to comparing women to a Barbie doll, he said.

"If both people are enjoying the experience, that's what matters," he said. "If it's five hours, great. If it's five seconds, great. Relax and have a good time and don't worry about how long it lasts."