The beneficial and well-being effects of human sexual arousal induced by coitus or masturbation are reviewed. Greater sexual satisfaction and some health rewards are given by coitally obtained orgasms even though those from masturbation may be more physiologically intense. The functionality of the circulatory, neural and muscular systems of the male and female genitalia are maintained by arousal and orgasm (maintenance functions) both in the conscious state and when asleep. Prophylactic actions (preventative functions) occur in relation to prostate cancer, implantation and dysmenorrhoea. In the male, ejaculations keep sperm morphology and semen volume within normal ranges while leukocyte numbers are increased. In the female, with coital vaginal deposition of semen mood enhancement occurs, menstrual cycles are more often of the ovulatory (fertile) type and postmenopausal vaginal atrophy is counteracted.