Say the word "secret" in the same sentence as the word "marriage" and, inevitably, catastrophe strikes.

How could my spouse hide this from me?

That he was married before. That she had a child out of wedlock. That he's a compulsive gambler. That she is, after all, a lesbian.

It wasn't until a year ago that Richard's wife told him she is "very attracted to women." They've been married eight years, parents to three girls ages 6 and under. Recently, the wife's girlfriend (both women are 28) moved in with them.

"Before we got married, I knew she'd never been with a man," says Richard, who thought his wife was a virgin. The 30-year-old engineer from Alexandria asked that his last name not be used. "But I didn't know she'd been intimate with other women. That was a secret she hid from me."

Of course secrets come in many forms, from the trivial ("I've got a mole on the back of my thigh") to the mundane ("I never told you I had a crazy cousin in New Mexico?") to the consequential ("Yes, honey, I did lose $20,000 in the stock market"), with variations in the gray areas in between. These days, New Jersey Gov. James McGreevey's secret -- "my truth is that I am a gay American" -- easily comes to mind.

"There are skeletons in most people's closets, and there are levels of trust," says Nancy Barskey, a Tenleytown psychotherapist who's specialized in couples counseling for 24 years. She's heard the secrets: a spouse who has herpes, a spouse who's been fired from his last four jobs.

"The spouse who's keeping the secret may feel there's a fault line in the relationship, a place that hasn't, for some reason, been touched upon," says Barskey. "The spouse might feel too vulnerable to reveal this secret. The spouse doesn't trust that the other person will be nonjudgmental."

Carol, 49, didn't know Jim, 45, was married twice before they tied the knot in her Baltimore home in November 1999. She also didn't know he had an estranged daughter, now 20 years old. She found out accidentally, when a sister of Jim's first wife learned he had remarried and called their home one afternoon, asking to speak with him.

She felt "embarrassed," "cheated," "fooled," "duped."

"My thinking was, 'If he kept this from me, what else did he and will he keep from me?' " says the accountant, who, like Richard, asked that her last name not be used. In many cases, the secret, once revealed, is interpreted as some sort of a lie, say psychologists Peter Pearson and Ellyn Bader, authors of the book "Tell Me No Lies: How to Stop Lying to Your Partner -- and Yourself -- in the 4 Stages of Marriage."

Pearson, 61, and Bader, 56, were married in 1982; two years later they founded the Couples Institute, which offers classes, counseling, workshops and seminars in Menlo Park, Calif.

"The person who's kept the secret -- for example, the husband who's into Internet pornography, that's a big one -- should choose Path A: You listen to the anger, distress and rage of your partner. You exercise more listening skills than you've ever done."

Bader cuts in. "You calm down. You have to stabilize the crisis."

For married couples with children, the stakes are higher, says Pearson. "You need insight and action; action without insight is impulsiveness, and insight without action is passivity."

So what can couples do?

"Seek a therapist," says Barskey, the Tenleytown psychotherapist. "What happens next depends on the strength of the marriage, the personalities of the people, their maturity, their resiliency, their ability to sit with some intolerable feelings and not be impulsive."

Obviously, compromises have to be made, say the experts, and some marriages, in fact, do survive. The Big Secret, of course, comes from all types of people: the introverts, the extroverts, the loving wife, the faithful husband. There is no precise, specific way to protect one's self from a secretive spouse, say the experts. Indeed, the hints that do come become clear after the fact -- with 20/20 hindsight. Richard, the 30-year-old father of three, says he had no clue. He and his wife are seeing a therapist. So far, it's helping. "Believe it or not, we are going to stay together," he says, but rebuilding the trust, he adds, "is an ongoing struggle."

The kids think the wife's live-in girlfriend is a "roommate."

"Our love for each other was never in question. Our preferences, clearly, are different. I wish I could have known this sooner, then I would have known what I was getting myself into, and I could have been with someone who's completely into me. But we got kids.

"Now, I have no choice."

Ellyn Bader and Peter Pearson, founders of the Couples Institute and authors of "Tell Me No Lies: How to Stop Lying to Your Partner -- and Yourself -- in the 4 Stages of Marriage."