Objective: To determine the efficacy and relative effectiveness of conjugated entrogens (CE) and fresh-frozen plasma (FFP) in normalizing prolonged preoperative bleeding times during renal transplantation. Design: Prospective, randomized trial. Setting: A university regional referral center for transplantation. Patients: Patients scheduled for renal transplantation with preoperative bleeding times greater than 10 minutes (normal, <7 minutes) following informed consent were asked to participate in the randomized protocol. Those with bleeding times of 8 to 9.5 minutes were asked, following informed consent, to be a control group receiving neither CE nor FFP. Interventions: Following induction of anesthesia and drawing of baseline laboratory tests, patients were administered randomly, using a table of random numbers, either 50 mg of CE or 2 U of FFP. Main Outcome Measures: Bleeding time measurements and other laboratory tests were repeated at the end of surgery as well as at 24 and 48 hours postoperatively. Results: Treatment with CE and FFP decreased the patients' bleeding times from 16.68±0.8 (SEM) and 17.13±0.85 minutes to 7.67±0.79 (P<.001) and 10.50±1.27 minutes (P<.001), respectively, by the end of surgery. At 24 and 48 hours postoperatively, the CE group had bleeding times of 9.77±0.99 and 9.81±1.24 minutes (P<.001 for both), respectively, whereas the FFP group bleeding times were 12.76±1.57 (P=.003) and 12.14±1.56 minutes (P=.001), respectively. There were no statistical differences for the control group compared with baseline either at the end of surgery or at 24 hours. Conclusions: Although both CE and FFP significantly decreased prolonged preoperative bleeding times during renal transplantation, CE might be preferred because of lower risk and cost, as well as a longer duration of action.