What's the only thing worse than finding out your man is cheating on you? According to the author of "The Straight-Up Truth About the Down-Low," it's finding out that he's stepping out on the side ... with another dude.

Despite what Hollywood would have you believe, such information is rarely the fodder for hilarious hijinks, a la the recent Chris Rock vehicle "Death at a Funeral." Instead, the realization that your man's been secretly playing for the other team all along can cause a special kind of devastation, according to Joy Marie, the book's author.

"If your man cheats with another woman, at least you have a chance to save your relationship," Marie says. "You can choose to forgive him, attend counseling sessions together and work on reestablishing trust in the relationship. And quite frankly, you can compete with another woman. If your man cheats with another man, your whole relationship was a lie. He was never attracted to you in the first place, and you definitely don't have the right equipment to compete with another man."

So what should you do if you have noticed a friend's significant other seems to you to exhibit telltale signs of being a Friend of Dorothy? Should you say something to her?

"Most definitely," says Joy Marie, who is actually two women, both of whom were on the losing end of men who were on the DL, or "down-low": guys involved with or married to women, while secretly having sexual relationships with men on the side.

"Take your friend to a quiet, private place," she advises. "Tell her how much you love and care about her and how much you value the friendship. Tell her your suspicions about her man's sexuality and why. Be prepared for her to be upset and to possibly even direct her anger at you."

According to Joy Marie, some telltale signs include "a lack of sexual desire, lack of intimacy, emotional detachment, constant criticism/abuse, hanging out with gay friends, watching gay porn, homophobic comments, mysterious telephone calls, admitting to past homosexual encounters, shaving body hair, etc."

Obviously, sexuality runs the gamut. In other words, don't confuse a lack of interest in beer and football or an addiction to self-tanning as surefire indicators that a guy is gay. Be aware that stereotypes are just that. Consider bringing up the issue with your friend in a caring manner if she has introduced her concerns over some of his behavior, seems concerned about the state of her relationship, or if you have really strong suspicions that cannot be quelled. Or if you've actually seen him making out with another guy.

Remember, "She may already have her own suspicions, but she will still feel shock, anger, betrayal, humiliation and pain," says the author. So you might want to make doubly sure that you're not confusing a healthy interest in Kathy Griffin and crochet with bona fide suspicions that he's cheating on her. "Just listen and let your friend know you will be there no matter what. Support her whether she chooses to leave or stay."

Have you ever suspected that a friend's significant other wasn't being, shall we say, straight with her? How did you handle it?