In 21 consecutive adult male patients with chronic renal failure on regular hemo- or peritoneal dialysis, the plasma levels of prolactin (hPr), growth hormone (HGH), thyrotropin (TSH), luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T) and sex hormone binding globulin (SHBG) were measured. Elevated levels of hPr were found in 16 of the patients and could not be explained by only the medication. All the patients studied showed an inverse ratio of LH to FSH with higher levels of FSH than LH and 15 of the 21 patients had elevated plasma concentrations of FSH, while only 4 had elevated LH. No significant difference in any of the hormone levels could be demonstrated before and after dialysis, and no significant correlation between the hormone levels and the time of dialysis, the type of dialysis or the age of the patient was found. Of the 21 patients, 8 showed higher levels of HGH before than after dialysis. Impotency was found in 11 of the patients, but was not related to abnormal levels of hPr, LH, FSH, T or SHBG.