The effect of Dicynene on blood loss during and after transurethral resection for benign enlargement of the prostate was studied in 76 patients. Median loss of blood at operation was 17 ml in those given Dicynene compared with 72 ml in the placebo group (p equals less than 0.001). Median postoperative blood loss was 38 ml in the Dicynene group, and 103 ml in the placebo group (p equals 0.05). Clinical evidence of deep vein thrombosis was found in neither group. Dicynene helps to reduce blood loss in transurethral resection.