An unhappy woman(Photo: Courtesy of Essence)

He seems so perfect. But then you get that feeling something's not right. Suddenly you're checking his pockets and his cell phone. The reality stops you cold: He's cheating. Many of us have been through this scenario, sometimes more than once, and with more than one man. When that happens, it's easy to think, Was there something I could have done? Was there something he said or did that could have tipped me off? Research tells us that some men are more inclined to stray than others, and a cheater often shows his hand well before the damage is done. Learn to read the signs and discover how you can protect yourself and safeguard your relationship.

Want to find a cheater? Check out his friends. "Seventy-seven percent of men who cheat have best friends who also cheat," says M. Gary Neuman, a family counselor in Miami, who surveyed 200 men for his best seller The Truth About Cheating: Why Men Stray and What You Can Do to Prevent It (Wiley, John & Sons). Neuman notes cheaters were also twice as likely as faithful men to have fathers who strayed. "These men live in a world where cheating is done. For them it seems normal," he says.

Protection Plan: Before you get into a serious relationship, find out your man's views on staying faithful, Neuman advises: "Does he have a cavalier attitude about infidelity, or does he have a very clear position that it's wrong and there is no excuse for it?" If your man thinks of straying as no big deal, that's a red flag that you two may not have the same ideas about what constitutes a commitment.

Cheaters lie. And often that duplicitous behavior begins well before an affair. You might catch him fibbing about his whereabouts or the company he keeps, or simply withholding information if he thinks you might disapprove. He'll tell you he's visiting his mother when he's really out with his boys or convince his boss he's at a funeral when he's headed to a ball game. "Notice if he's lying about simple stuff like running late to pick you up," says Washington, D.C., relationship expert Audrey B. Chapman, author of Getting Good Loving (Agate). "If he isn't truthful about the things a healthy person would be able to take ownership of and say, 'I'm sorry,' then you're in trouble."

Protection Plan: A man who lies with ease should not be readily trusted. "Depending on how severe the lie is, you either back away from him immediately or make it clear that he needs to be straight with you," says Neuman. "If he continues to lie after that, I wish you the best if you choose to stay in that relationship."

Men respond to danger, including a failing economy, with a heightened interest in short-term sex, according to researchers at the University of Kansas. "This happens at an unconscious level," explains Omri Gillath, Ph.D., lead author of the study. Experts believe this behavior is designed to ensure the survival of our species. The impulse is the same whether the threat is a pack of lions or impending economic doom.

Protection Plan: If your man has lost his job or is facing foreclosure, "reduce his anxiety by showing him he's loved and supported," advises Gillath. "Being a safe haven for each other is good advice for any relationship."