Sexual function in 24 patients with major affective disorders who were given prophylactic lithium treatment was compared with that of a control group of surgical outpatients with no known psychiatric disease. Changes in sexual function during lithium treatment were also recorded retrospectively. Sexual dysfunctions were described by about one-fourth of both female patients and controls. About one-third of the male patients and controls reported sexual dysfunctions. We cannot exclude tha lithium in combination with other psychotropic drugs may increase the frequency of sexual dysfunction. Changes in sexual function during lithium treatment were reported by one-fourth of the patients. Of these, four reported a positive influence of the treatment and five a negative influence. Statistically, significantly more patients than controls were dissatisfied with their present sex life.