The purpose of this paper was to identify the circumstances associated with casual sex encounters, as well as to identify the link between casual sex, depressive symptoms, and infidelity among college students. We found that casual sex was a fairly common occurrence that was related to early sexual transition, engaging in first sex with a casual sex partner, drug use and alcohol consumption. Casual sex occurred more often between "friends" rather than with strangers. Depressive symptoms were associated with engaging in casual sex differently for males and females. Males who engaging in casual sex reported the fewest symptoms of depression and females who had a history of casual sex reported the most depressive symptoms. Frequencies of affectionate and genital behaviors were associated with expectations of the relationship, the relationship to the partner, infidelity, and the individual's relationship style. Results are discussed in light of evolutionary and socio-cultural theories of sexuality.