WASHINGTON - The generation that promoted free love has grown old and cranky about sex.

Faced with performance problems, menopause blues and an increased mismatch of expectations between the sexes, baby boomers are the unhappiest Americans of all when it comes to making love, a new Associated Press-LifeGoesStrong.com poll shows.

Only 7 percent of people between 45 and 65 describe themselves as extremely satisfied with their sex lives. And nearly a quarter of the boomers say that they're dissatisfied.

The findings represent a stark turnaround for the group of Americans who spearheaded the sexual revolution, coming of age as birth control became readily available, premarital sex gained wider acceptance and abortion was legalized. The boomers also were many of the first victims of the AIDS epidemic.

Younger and older people report better feelings than do boomers about their sex lives. Some 24 percent of boomers say that they're dissatisfied, compared with only 12 percent of 18- to 29-year-olds, 20 percent of those 30-44 and 17 percent of those 65 and older.

Perhaps the boomers have given up on experimenting. A surprising number of baby boomers feel that they've learned just about all there is to know about sex - nearly three in five women and half of men.

But if women are wiser, men are more disgruntled. Twenty-eight percent of men between 45 and 65 are dissatisfied, and more than two in five say that their sex lives got worse in the past decade.

Part of the explanation seems to lie in different sexual expectations. Men are often more eager - at least mentally, if not physically - as more women become uninterested. Nearly half of the men say that their partners don't want sex often enough, while only 17 percent of women feel similarly let down.

The story is different when it comes to action, as men are the underperformers. The poll finds that two in five men between 45 and 65 having problems with sexual functioning. Only 19 percent of female boomers say the same. For both genders, less than half received treatment.

"Men certainly do tend to have higher sex drives," said Debby Herbenick, of the Center for Sexual Health Promotion at Indiana University.

She noted that while some women maintain high sex drives, boomers tend to go into menopause. This can hamper sex lives, as hot flashes and tiredness replace feelings of passion in women.

But Herbenick dismissed the notion that baby boomers had nothing left to learn: "I don't think a single person in the whole world knows all there is about sex."

Sex therapist Ruth Westheimer blamed the male/female mismatch on mass culture and its misleading messages about a healthy sex life, especially for aging men. "The media makes it sound as if everybody should have sex from morning to night," she said. "That's not realistic."

One of the starkest differences between the sexes deals with fantasizing. Seventy-two percent of the boomer men said they thought about having sex with someone other than their sexual partner at the time. Less than half of the women admit similar mental wanderings.

Still, a slim majority of boomers say that they can have a strong relationship without sex.

The AP-LifeGoesStrong.com Poll was conducted Oct. 1-10 by Knowledge Networks of Menlo Park, Calif. It involved online interviews with 945 people between 45 and 65, as well as companion interviews with an additional 587 people ages 18-44 and 65 and older. It has a margin of sampling error of plus or minus 3.5 percentage points for all adults, 3.9 percentage points for adults 45-65.