Forty-seven men (median age, 31.5 years) were studied prospectively to assess the effect of Hodgkin's disease and subsequent chemotherapy on gonadal function. Before therapy, 16 (43%) of 37 men were functionally subfertile, as assessed by impotence (four of 37) and "inadequate" sperm counts (12 of 37). Histological abnormalities were noted in eight of nine pretreatment testicular biopsy specimens. Additionally, changes were noted in blood hormone levels and libido. After completion of only two cycles of chemotherapy, 14 of 14 men became persistently azoospermic, with blood follicle-stimulating hormone levels four to five times normal. Posttreatment testicular biopsy specimens confirmed germ cell aplasia. During therapy 17 (81%) of 21 men had mild or no libido; irritability in 16 (84%) of 19 and violence in four (18%) of 22 caused additional family distress. While it is clear that cytotoxic therapy induces infertility, these data further indicate that a proportion of men have gonadal dysfunction prior to treatment.