The ladies of "Sex and the City" (search) finally found their partners, but there’s a good chance that Carrie and her pals will be single again in another 20 years.

A growing number of middle-aged Americans are single — 34.6 million over 45 years old, according to Census (search) figures — due to being widowed, divorced, separated or never married. Now these mature daters are coming out from behind the veil that once hid graying singles who thought dating was only for the young.

"The fastest growing group is singles over 50," said Rich Gosse, Chairman of American Singles. "That group is becoming humongous, and it's been ignored for so long."

Matchmaking Web sites and services are starting to recognize these romance seekers. Match.com said there’s been an 88 percent increase in the number of members over 50 in the last year. And one of 2003's surprise hits was "Something’s Gotta Give," a romantic comedy about two middle-aged people finding love, starring Diane Keaton (search) and Jack Nicholson (search).

"I think the film was hopeful for people meeting later in life. [Keaton] was a character my friends and I could relate to," said Sharon Guy, a 50-something professional who got divorced in 1981.

While Carrie Bradshaw and friends stumbled through disappointing dates wondering if their lives would ever include marriage and children, most over-50 daters have been there, done that. Instead of looking for someone to start a life with, they're looking for someone to share an already established life with.

"Singles who are 55+ are least likely to say they are looking for marriage," said Match.com's vice president of romance, Trish McDermott. "I think most of them have come from a long term relationship or a marriage ... They want companionship and romance and passion, then will see where it goes."

Yet, dating later in life is fraught with its own set of hurdles and criteria.

For one thing, older women rate sex as their No. 1 priority in a mate, while men pine for a woman who shares their interests, according to Mason Grigsby, co-author of "Love at Second Sight: Playing the Midlife Dating Game."

"Men are, contrary to what women believe, becoming more mature," said Grigsby. "Women say guys never change, but yes we do. You can't go out and roam around anymore because all your friends are married or gone. You can’t go out and drink late because you don’t have enough energy."

Grigsby, who doesn’t sugarcoat the facts of life after a certain age, said playing hard to get isn’t worth the time at this stage.

"Don't worry about rejection. You're going to be dead soon. That's the theme of the book," said Grigsby. "The boat's leaving the dock. You don't have time to wait around."

Grigsby, who surveyed 400 singles over age 50 as part of his research, said as they age, men in particular are looking for stability.

"What's really significant for men — and women — is what they most value now, things which weren't in the picture when they were younger: good health and friends are at the top."

In that vein, services for older singles are ramping up. Gosse recently hosted a Midlife Singles Convention, which he said drew 200 people from the San Francisco Bay Area. There are also dating Web sites such as the personals on thirdage.com and seniorfriendfinder.com specifically for older people.

Still, Guy said she'd rather meet a man the old fashioned way, through friends and common interests, though she has tried Internet dating.

"A lot of women in my age group, if they’re not working women, they may not even have a computer," she said. "But it is part of the decision people make, like 'I’m going to find someone,' and [the Internet] is one of the tools."

Grigsby found that what singles are looking for in a partner changes as people age, but Guy said her essential list of qualities hasn't altered drastically.

"I think the things that attract me to someone have stayed quite consistent through the years: shared values, emotional availability and a desire to partner, to team up, to do life together," she said.

And though Guy would like to remarry (her ex-husband remarried quickly after their divorce) she said she's realistic about her prospects.

"I would love to have that dream I had as a girl. Then reality sets in and people want companionship, someone to travel with, the practical things," she said.

The practical things singles over 50 are looking for run the gamut, said Gosse, from financial stability to someone to care for them when they get older.

"People think ... 'I’m getting older, I might get sick and I don’t have anyone to take care of me. I better get married,'" he said, adding that young daters have entirely different things on their minds.

"Young men are thinking about getting [sex] and young women are thinking about getting babies," he said. "The midlife ballgame is totally different from the early life ballgame."