This prospective, randomized study evaluated the effects of spinal versus general anesthetic technique on perioperative blood loss and the development of postoperative coagulopathies in 50 patients undergoing transurethral resection of the prostate (TURP). Preoperative hematologic measurements included hemoglobin, platelet count, electrolytes, prothrombin time, partial thromboplastin time, fibrinogen, factor V, plasminogen, antithrombin III, and fibrinogen degradation product (FDP) levels. All hematologic blood samples wre repeated postoperatively at 1, 6, and 24 h. Intraoperative blood loss was not significantly different between the spinal and general anesthesia groups. The total blood loss after TURP was significantly correlated (r = 0.76; P < 0.0001) with the prostatic tissue weight. When the tissue weight resected exceeded 35 g, blood loss was in excess of the linear correlation shown with the weight of resected prostatic tissue. Platelet count decreased and prothrombin time increased in the spinal group at all postoperative time intervals compared to preoperative value (P < 0.05). There was no significant difference in measured coagulation variables (fibrinogen, factor V, plasminogen, antithrombin III, and FDP) between the spinal and general anesthesia groups, but there were significant decreases in postoperative fibrinogen and Factor V levels compared to preoperative values in both spinal and general anesthesia groups. Three patients (6%) had increased FDP levels 1 h postoperatively. The prostatic tissue weight and the surgical duration was significantly higher in these patients. We conclude that perioperative blood loss in TURP patients is not affected by the anesthetic technique. However, 6% of TURP patients developed subclinical intravascular coagulopathies which correlated with mass of resected prostate tissue.