Recombinant human erythropoietin (rHuEPO) was administered to males undergoing hemodialysis, and its effects on penile erection and hypothalamus-pituitary-gonadal hormone levels were studied. The subject consisted of 18 males undergoing hemodialysis ranging in age from 22 to 58 years (mean 45.3 years). Chronic glomerulonephritis was present in 16, and diabetic nephropathy in 2, as underlying disease. rHuEPO was administered intravenously at 1,500 U 3 times a week with a target to increase the Ht value to 25% or above. Penile erection was evaluated subjectively by a questionnaire based on a visual analogue scale and objectively by semi quantitative measurement of nocturnal penile tumescence (NPT) using an erectometer. Of the 18 patients, subjective improvements in penile erection were observed in 13 (72%), and objective improvements in NPT were observed in 10 (56%). The administration of rHuEPO may alleviate hyperprolactinemia but was found to have no effect on the FSH, LH, Zn, or HS-PTH level. rHuEPO was suggested to be fairly effective for the treatment of sexual disorders.