The New Infidelity; Overworked and underappreciated, more American wives are seeking comfort in the arms of other men.

Byline: Lorraine Ali and Lisa Miller (With Vanessa Juarez, Holly Peterson, Karen Springen, Claire Sulmers, William Lee Adams And Raina Kelley)

When groups of married mothers get together, especially if there's alcohol involved, the conversation is usually the same. They talk about the kids and work--how stressed they are, how busy and bone tired. They gripe about their husbands and, if they're being perfectly honest and the wine kicks in, they talk about the disappointments in their marriages. Not long ago, over lunch in Los Angeles, this conversation took a surprising turn, when Erin, who is in her early 40s and has been married for more than a decade, spilled it. She was seeing someone else. Actually, more than one person. It started with an old friend, whom she began meeting every several months for long dinners and some heavy petting. Then she began giving herself permission to flirt with, kiss--well, actually, make out with--men she met on business trips. She won't have sex with anyone except her husband, whom she loves. But she also loves the unexpected thrill of meeting someone new. "Do you remember?" She pauses. "Do you remember the kiss that would just launch a thousand kisses?"

Erin started seeing other men when she went back to work after her youngest child entered preschool. All of a sudden she was out there . Wearing great clothes, meeting new people. Veronica, on the other hand, fell in love with a man who was not her husband while she was safely at home in the Dallas suburbs looking after her two children. Married to an airline pilot, Veronica, now 35, took up with a wealthy businessman she had met at a Dallas nightclub. Her lover gave her everything her husband didn't: compliments, Tiffany jewelry, flowers and love notes. It was, in fact, the flowers that did her in. Veronica's lover sent a bouquet to her home one afternoon, her husband answered the door and, in one made-for-Hollywood moment, the marriage was over.

Much has changed since Emma Bovary chose suicide with arsenic over living her life branded an adulteress--humiliated, impoverished and stripped of her romantic ideals. In the past, U.S. laws used to punish women who cheated; in a divorce, an unfaithful wife could lose everything, even the property she owned before marriage. Newer laws have been designed to protect these women. The reality is this: American women today have more opportunity to fool around than ever; when they do fool around, they're more likely to tell their friends about it, and those friends are more likely to lend them a sympathetic ear. If they do separate from their husbands, women, especially if they're college-educated, are better able to make a go of it--pay the bills, keep at least partial custody of the children, remarry if they want to--than their philandering foremothers. "It was just so ruinous for a woman to be caught in adultery in past times, you had to be really driven or motivated to do it," says Peter D. Kramer, clinical professor of psychiatry at Brown University and author of "Should You Leave?" "Now you can get away with it, there's a social role that fits you."

Just how many married women have had sex with people who are not their husbands? It's hard to say for sure, because people lie to pollsters when they talk about sex, and studies vary wildly. (Men, not surprisingly, amplify their sexual experience, while women diminish it.) Couples' therapists estimate that among their clientele the number is close to 30 to 40 percent, compared with 50 percent of men, and the gap is almost certainly closing. In 1991 the National Opinion Research Center at the University of Chicago asked married women if they'd ever had sex outside their marriage, and 10 percent said yes. When the same pollsters asked the same question in 2002, the "yes" responses rose to 15 percent, while the number of men stayed flat at about 22 percent. The best interpretation of the data: the cheating rate for women is approaching that of men, ...