Oral estrogens decrease bleeding time and improve clinical bleeding in patients with renal failure. PURPOSE: A prolonged bleeding time is associated with platelet dysfunction and clinical bleeding in patients with renal failure. Parenteral estrogens have been shown to shorten the prolonged bleeding time in patients with chronic renal failure, although the mechanism of action is unknown. We conducted a study to evaluate the efficacy of oral conjugated estrogens in this setting. PATIENTS AND METHODS: Four patients with renal failure, prolonged bleeding time, and clinical bleeding were given 50 mg of conjugated estrogen (Premarin) daily. RESULTS: Bleeding time normalized in two cases and was reduced to less than 50% of the pretreatment value in one of the remaining two cases. Bleeding stopped in all patients within two days. Ten dialysis patients with prolonged bleeding time were randomized to a course of 50 mg of Premarin daily or placebo. The bleeding time in all five patients in the Premarin group normalized or decreased to below 50% of the pretreatment value after 7.0 +/- 4.2 days of therapy. The bleeding time did not normalize in the five patients treated with placebo. No side effects attributable to therapy were reported. CONCLUSION: We conclude that orally administered conjugated estrogens effectively improve the bleeding tendency in patients with chronic renal failure. 