We selected a group of male dialysis patients complaining of sexual dysfunction in whom penile vascular insufficiency and drug-induced impotence had been excluded. Monitoring of nocturnal penile tumescence was used to confirm organic disturbance. Patients with normal serum prolactin concentrations (n = 18) had significantly lower serum zinc values than normal controls (P less than 0.001) and were entered in a 6-month double-blind study comparing oral zinc acetate with placebo. Patients with elevated prolactin concentrations (n = 8) were entered in a 3-month double-blind crossover study comparing oral pergolide mesylate with placebo. In the zinc study, serum zinc concentrations increased (P less than 0.05) in the zinc-treated but not the placebo-treated group. One of nine patients receiving zinc reported improved sexual function, as did two of nine patients receiving placebo. There were no significant changes in sperm counts, nocturnal penile tumescence, testosterone, sex hormone binding globulin or gonadotrophin concentrations in either treatment group. In the pergolide study, serum prolactin values decreased (P less than 0.01) in the pergolide but not in the placebo treatment period. One patient reported improved sexual function during the pergolide treatment period and two during the placebo period. There were no significant changes in sperm counts, nocturnal penile tumescence, testosterone, sex hormone binding globulin or gonadotrophin concentrations after pergolide. These studies show no benefit of zinc or pergolide compared with placebo in the treatment of uraemic impotence.