Between November 1990 and March 1992, 150 patients at 10 United States institutions were treated with transurethral ultrasound-guided laser-induced prostatectomy (TULIP) for the relief of bladder outlet obstruction secondary to benign prostatic hypertrophy. The TULIP system incorporates ultrasound visualization with a 90-degree angle, side-firing laser to effect coagulation necrosis of prostate tissue. The overall preoperative prostate volume in this TULIP study was 40 cc and all types of prostatic enlargement, including median lobe obstruction, were treated. There were no intraoperative complications, with no hemorrhage or post-transurethral resection syndrome, and no blood transfusions were required. Hospital stay averaged 1.7 days and 83% of the patients went home after a 1-night stay. We evaluated 63 patients at 6 months after the TULIP procedure. Mean symptom scores decreased from 18.8 to 6.1, for a 68% improvement. The mean peak flow increased from 6.7 ml. per second preoperatively to 11.9 ml. per second, for a 78% improvement. Overall, 87% of the patients exhibited at least 50% improvement in either the symptom score or peak flow parameter, while 49% of the patients demonstrated at least a 50% improvement in both parameters.