As the oldest boomers turn 60 this year, more of them are single than any previous cohort of forty- to sixtysomethings, reports Senior Editor Barbara Kantrowitz. And while this generation's search for love and relationships is anything but new, what has changed is how they meet, why they date and how society responds. In this latest installment of its yearlong series

"The Boomer Files," Newsweek looks at the new world of midlife romance.

A generation ago, older singles were out of the game, but now, boomers are flaunting their sexuality. "It's a situation of enjoying what's there," says Helen Gurley Brown, whose 1962 book "Sex and the Single Girl" ushered in a new era of openness about women and desire.

"Sex is such an enjoyable activity at any age," says Brown, 83. "Why delegate it only to the young?"

But while they are looking for companionship in record numbers, many boomers aren't eager to settle down. American women in their 40s and 50s are better educated and more affluent than any previous generation of women at midlife, and that has transformed the way they view dating. In a recent AARP study, only 14 percent of women said their most important reason for dating was to find someone to live with or marry, compared with 22 percent of men.

College professor Katherine Chaddock, 58, coauthor of "Flings, Frolics and Forever Afters: A Single Woman's Guide to Romance After Fifty," has a full schedule with work, her kids' visits home from college, and her trips to the gym. For now, Chaddock says, her ideal relationship would be a "flex time" romance.

"I could really enjoy on a fairly long-term basis somebody who lives and works about 100 to 200 miles away, somebody I saw every weekend, Friday through Sunday," she says.

"Then we'd take a break and I could go back and talk to my cats and do silly stuff and wear my teeth-whitener strips around the house."

In past generations, the assumption was that men could readily date down the calendar while women couldn't. But those rules have also changed.

Joe Germana, 49, began dating a woman nearly ten years younger, in a relationship that included lots of passion and lots of late nights. Paradise? Not exactly.

"The lifestyle was killing me," Germana says. "I'm not used to all those late nights." The relationship quickly fizzled. "She needed someone younger andmore exciting," he says, "and I needed a break since I was half dead."

Or think of the groundbreaking affair between Samantha Jones, the aggressive publicist on "Sex and the City," and her gentle boy toy, Smith Jerrod. In real life, Kim Cattrall, the 49-year-old actress who played Samantha, is in a relationship with 27-year-old Alan Wyse, a private chef whom she describes as an old soul.

After playing a sexually adventurous character, Cattrall found it hard to have a relationship with a man her own age because she thought they were trying to compete with Samantha. A younger man, she says, doesn't feel that need to outdo her.

"The thing I really enjoy," she says, "is that I can show him my world and what I think about something. He's not closed down."

Though single boomers are having sex regularly, only 39 percent invariably use protection, according to the AARP study. "To me, those are pretty alarming figures," says Linda Fisher, AARP's research director. Many boomers just don't have a sense of danger about sex. They came of age before the HIV epidemic and never learned how to negotiate condom use or testing with their partners.

The number of new HIV infections among older women is rising rapidly: between 1998 and 2000, women's share of AIDS cases among those 50 and older nearly doubled, from 8.9 percent to 15 percent.

The way boomers meet is also changing. While many still meet the old-fashioned way-through friends, neighbors or relatives --a growing number are searching online.

Jim Safka, CEO of Match.com, says that people over 50 make up his site's fastest-growing segment, with a 300 percent increase since 2000.

Some sites, like PrimeSingles.net, cater specifically to the over-50 crowd.

"Even 25 years ago, most people were reliant on their friends to fix them up," says family historian Stephanie Coontz, of the Evergreen State College in Washington. "People in their 40s and 50s don't want to be hanging out at bars.

Now they have access to this incredible pool of single people their age."

Also included in the "Sex & the Single Boomer" cover package:

* Now that Baby Boomers' youthful rock-and-roll romances are over and the       kids have grown up and taken the SAT, it's time for Marriage, Act II --      and it's not always a pretty picture, reports Senior Writer Claudia       Kalb.

The stressors that strike, from health crises to layoffs to       infidelity, are emotionally and financially painful, and plenty of relationships have crumbled because of them. The key to those who succeed? Flexibility and humor and affection.

* As boomers move through their middle years, many are delighted to find that they have a friend -- sometimes a network of friends -- who is every bit as close as their own brothers and sisters, reports Senior Writer Peg Tyre. Psychologists call the phenomenon "family by choice," and say it is an inevitable -- and healthy -- response to 40 years of social upheaval.