Sexual dysfunctions are common among patients with chronic renal failure. The prevalence was assessed in a population of 281 patients (20-60 years), and it was attempted to determine whether their mode of treatment (haemodialysis, peritoneal dialysis, or kidney transplantation), or biochemical and endocrine variables and neuropathy affect sexual functioning. Patients with rheumatoid arthritis served as a comparison group. Assessment included clinical history, physical and laboratory examinations, questionnaires measuring erotosexual dysfunctions, and a psychophysiological test procedure. The latter is a laboratory method which measures, in a waking state, subjective and physiological sexual arousal. Men on haemodialysis or peritoneal dialysis suffered significantly more often from 'Hypoactive Sexual Desire Disorder', 'Sexual Aversion Disorder' and 'Inhibited Male Orgasm' than men with kidney transplantation or rheumatoid arthritis. Interestingly, the prevalence of 'Male Erectile Disorder' did not differ significantly between the four groups and ranged between 17 and 43%. Of the women, transplanted patients suffered significantly less from 'Hypoactive Sexual Desire Disorder' than the other three groups; the prevalence of other sexual dysfunctions did not differ between the groups. Although 'Male Erectile Disorder' and 'Female Sexual Arousal Disorder' had a relatively high prevalence there were no differences in the four groups of patients in genital responses during psychophysiological testing. Genital responses during psychophysiological assessment had no relationship to the duration of renal replacement treatment, biochemical/endocrine variables, or the presence/ absence of neuropathy. The prevalence of sexual dysfunction was high. Sexual dysfunction in men on haemodialysis or peritoneal dialysis was not so much due to erectile failure but largely to loss of sexual interest, subjectively ascribed to fatigue. The latter was also found in women on haemodialysis or peritoneal dialysis.