Any number of reasons are possible. Desire for something new, curious, bored, wanting to find out if he still can attact a woman. Could be as simple as the opportunity presented itself. The bottom line is there can never be one answer. Even if you asked the guy he might not be able to say. A reply or "it just happened" might not be very far from the truth. Often, I am sure, it has nothing to do with the woman in the 20 year relationship.

Depends on what you believe as far as psychology and such goes. From my beliefs, based on reading and research and my own personal observations, both man and woman have a basic set of needs, but they are both mutually different. The book 'His needs Her needs' (Willard F. Harley) is very good in outlining these. I can't remember off the top of my head, but a man's basic needs were sexual fulfilment, for his wife to admire him, to be his playmate and several other things. The woman's main needs were affection, communication and security... Like I said, I can't remember them all. If a husband or wife are not getting their needs met, they can be tempted to look elsewhere. If you stop for a minute and look at it from that perspective, can you think of any needs that have not been met that may have led him to find another woman? Sexual fulfilment or admiration? Does he and his wife have a good sexual relationship? What about admiration? Does she encourage or criticise? Another book, 'Love and respect', (Emerson Eggerichs) states that a woman needs unconditional love, while a man needs unconditional respect. Again, this comes down to the encouragment/criticism thing. From what the author states, women see criticism and conflict as a way to bring the relationship closer by discussing and reaching a resolution. Men don't see it that way. Criticism is seen as an attack on their honour, and the worst form of disrespect. His code of honour says that he should not retaliate, so he closes down, or stonewalls himself. That silence is the opposite of what the woman is trying to achieve, and suddenly she feels unloved, while he is feeling disrespected. The author calls it the 'crazy cycle'. Obviously there is an issue, and unless he had deliberately decided from the outset that he's going to sleep around, the issue involves both him and the wife. It says that although the relationship may have looked fine on top, that there is indeed a deep problem. The other theory I look at is the "love bank" theory. Each person has a love bank, and the other people they interact with have accounts in that bank. What they do will either add or subtract from that account. Obviously, at one time or another, the man and his wife had built up their accounts in each others' banks to the point where they wanted to be married. What state are the love accounts in today? What state were they in before the affair? The problem here is that if another woman comes in and starts building an account in his love bank, it will get to the point where it rivals or exceeds that of his wife. This is a place of extreme danger for him, because now he will feel that he 'loves' this other woman more than his wife, and will be tempted to go to her. My answer, after all of this psychobabble, is that there is a real possibility that her attention and admiration and infatuation with him filled a need that wasn't being filled, and he has gone in search of that. Be it respect or admiration or sex... these are all very real needs in a man's life. Obviously I don't condone what he's done, but at the same time I do not seek to lay the blame entirely on him. Unless he's premeditated it, it is a reaction to what is around him, and his own emotional state. If this is an actual case, alot of work and forgiveness need to flow in order to rescue this relationship. Punishment and guilt will not stop him - it will make him resent and feel condemned. He needs to be brought back from where he is, because as wounded as the wife may be, I can tell you that he is wounded as well. I would suggest finding a good marriage counsellor (in my preference, an experienced Christian one), and be willing to work through the issues. The wife needs to work through hers and reach a state of forgiveness, and the man needs to work through his and find forgiveness. This is the only way that things will reconcile themselves... My 2c worth, for what it's worth...

Boredom, need for excitement, variety. Do you read the same book every night?

I agree with Shabba. Emotional and physical needs are not being met. The other woman is meeting his emotional and physical needs... for now. But it won't last. Affairs are what they are.

One more thought on this one from me. In my opinion, both the cheating spouse and the victim spouse are responsible for the affair. There had to be some kind of warning signs, arguments, actions that started before the affair began. I had an affair with a married man and I am married as well. He has been married for 11 years and I have been married for 21 years. According to my ex lover his wife was bossy, demeaning, spent his money, put all of her effort into their only child and denied him sex. He said his friends say he acts like a total different person when she is around him, he can't be himself. I believe him, because my friends and I know his wife and she is just not a nice person to anyone. Now with that being said, maybe she was unhappy because of things HE was doing and she was just mean to everyone becuase she was miserable. I don't really know how he is at home. I never saw him day in and day out. But all I can say is that when she discovered me thru his phone bill, boy did she change her tune! It was OK for her to take advantage of him UNTIL she found out there was another woman. He may not have expressed to her ALL of his needs, but come on! She should know that is not exceptable behaviour. You don't treat ANYBODY that way. Eventually, if you keep it up the person will retaliate...thus an affiar is born. My ex lover and I both hurt our spouses horribly and our spouses hurt us as well. But now I am happy to report that both of our marriages are saved and I feel mine is getting stronger everyday. The doors of communication are always open. I REFUSE to go down the Road of Infidelity again and so does my ex lover.

The question is, why would a married man cheat on his wife period!!! You can talk about needs not being met, bordom, anything that you can think of, this is still NO excuse...NONE. I have experienced this first hand, I never gave my wife any reason for cheat on me, I never say it comming, no clues..nothing. Get a divorce, then go play the field. I am sorry if I come across harsh or brazen, but this just strikes a nerve with me....

I would say he lost his mind. I can't provide a good reason unless maybe she hypnotized him and the rest was history.

Complete suspension of all rational thought and reason.

A range of reasons are possible. Perhaps it was a spur of the moment decision that he now regrets, or perhaps he believes his emotional and/or sexual needs are not being fulfilled. It won't last, and these things never do, however, it can be hard to accept and come to terms with the damage caused to a relationship from such an affair. I think the wife should sit down and work out the issues with the man and see what needs to be fulfilled and then work to make the conclusions work out.

two words - selfishiness and self-indulgence. it's not you, he has a major attitude!

Perhaps he fell in fell in love with other women unintentionally?!?!?!

Well, he's been married to the same woman for 20 years. If they still have sex, it's probably pretty predictable. She likely takes him for granted, doesn't find him very exciting anymore, and certainly doesn't fawn over him. Then he meets a woman who is enticing, who seems to like him, it's all new, fresh, adventuresome. Damn, I'm gonna go find me one!

For a bit of excitement of course

because he is stupid. there is no pshycological explanation...hes just stupid.

Wow, that's hard to answer with no history. It could be allot of different reasons. Sometimes people grow apart. I know that there are men that go threw midlife crises. probably women to, but I know my father, and my father in law did. Maybe they lost each other in those 20 years. A marriage don't stay together by the number of years that have past, but by what those years brought to them as a couple. I believe if a man is feeling low on self esteem then he looks for something or someone to boost his esteem. This don't make it right...IDK If there was a concrete answer someone would be rich and all the cheating men would be fixed.....