According to research published in the August issue of Archives of Sexual Behavior in a survey of 400 students and volunteers, the following top 20 reasons were given by men as to why they have had sex in the past:

1. I was attracted to the person.
2. It feels good.
3. I wanted to experience the physical pleasure.
4. It’s fun.
5. I wanted to show my affection to the person.
6. I was sexually aroused and wanted the release.
7. I was ‘‘horny’’.
8. I wanted to express my love for the person.
9. I wanted to achieve an orgasm.
10. I wanted to please my partner.
11. The person’s physical appearance turned me on.
12. I wanted the pure pleasure.
13. I was ‘‘in the heat of the moment’’.
14. I desired emotional closeness (i.e., intimacy).
15. It’s exciting, adventurous.
16. The person had a desirable body.
17. I realized I was in love.
18. The person had an attractive face.
19. The person really desired me.
20. I wanted the adventure/excitement.

Keep in mind, most of the subjects were college students, which certainly might color why some of these are in the Top 20.

See also, Top 20 Reasons Women Said They Have Sex and the full list of 237 reasons to have sex.