This paper examines the potential effectiveness of a high power, 810 nm diode laser in inducing thermal coagulation of prostatic tissue. A theoretical study is performed to compare the effectiveness of the diode laser with the currently used Nd:YAG laser (1064 nm) for prostrate coagulation. Transurethral diode laser irradiation in a canine model is also performed to examine the efficacy of inducing thermal coagulation in vivo. Model results show that comparable tissue effects can be obtained with both diode and Nd:YAG lasers. The in vivo results indicate that considerable amount of coagulation necrosis of prostatic tissue can be induced by the high power diode laser.