would you tell your friend?

I wont tell him. Because I might be the one his girlfriend is kissing with. Well I think they have to discover it themselves, I really dont want to interfere with them even if they are my friends. Perhaps I would just ask my friend, if she/he really love his/her partner. Maybe he/she is also just fooling around or kissing others also, what do you think?

I will. By hiding it, I am giving her an additional pain when she will find it out.

I would have to tell as well. HOWEVER always know that when you tell a person something like this, unless they are a very close friend, they will most likely get mad at YOU.

To tell he immediately .I think he or she will be injured sooner or later if his/her partner loved another,better tell him and ease his pain ,otherwise he will be hurted more than now.....

I would also tell my friend. In a lot of my friend's relationships though, I am friends with both of them, so it would be hard. I do not believe in cheating, period. There is always the option of not doing anything, so I really don't understand cheating to begin with. Back to your question though, even if I were closer to the friend doing the cheating, I would still confront them(later, not while they are actively engaged in the cheating). I would give them the option to come clean to their significant other first, and if they didn't, then I would do it for them.

Me, too. It would be devastating to her if I did not tell her sooner. Because she is my friend, I don't want her bf/gf cheating on her. I would tell her and helped her until the healing process.