The effects of hormone treatment of transsexuals on the emotional state and sexual feelings have been studied less extensively than the effects on physical appearance and functioning. Most of the research in the field of hormone-behavior relationships has been carried out in non-patient groups or in patient groups other than transsexuals. Results of the few available studies of transsexuals are generally consistent with this research. In the existing literature the following hormonal effects on sexuality are reported; an enhancement of sexual interest, fantasies and initiative after androgen administration in female-to-male transsexuals; a loss of sexual interest as well as a loss of erections and the capacity to reach orgasm in male-to-female transsexuals after the use of antiandrogens. Less thoroughly investigated are the effects of hormone treatment on moods. In transsexuals, the following effects are reported: in male-to-female transsexuals less feelings of tension and more feelings of relaxation after anti-androgen intake and a calming down of emotional disturbances after estrogen intake; a greater sense of wellbeing in female-to-male transsexuals using androgens. No systematic effects of androgens on aggression and anger were found. Non-androgen factors appear to be more important determinants of aggression than androgens.