Psychosexual dysfunction is often suggested the cause of the disturbed eating habits associated with hypothalamic secondary amenorrhea.In contrast, we explored the possibility that impaired sexual function may result from reduced levels of testosterone in amenorrheic subjects as a consequence of particular lifestyles. We studied the effects of erotic stimuli in two experiments, one comparing amenorrheic women to normal controls, the other comparing testosterone substitution to a placebo treatment. The amenorrheic women had a higher incidence of lifestyle and bodily conditions identified as risk factors for amenorrhea (i.e., weight loss before the onset of amenorrhea, low body weight, strenuous exercise, and vegetarianism), lower levels of testosterone, and impaired sexual function compared with normally menstruating women. In an experimental session in which amenorrheic women were asked to produce erotic fantasies, they demonstrated a reduced capacity for sexual fantasizing, less subjective sexual excitement, and less vaginal vasocongestion (vaginal pulse amplitude). However, when exposed to the stronger of two erotic film excerpts, the degree of vaginal response of the amenorrheic women was comparable to that of normally menstruating women. Subsequently, we showed that treatment with testosterone increased vaginal vasocongestion in the same amenorrheic women during exposure to the most potent visual stimulus but had no effect on subjective sexual experience. Testosterone substitution influenced physiological aspects of sexual function, but the psychological level remained unaffected.