Penile erectile dysfunction is often attributed to abnormalities of vascular supply or drainage, but few direct measurements of penile blood flow have been made, and there is no established normal range. This study was undertaken to establish normal range of hemodynamic parameter of potent men. Data were acquired in frame mode after intracorporeal injection on one side of midshaft in variable state of 0.1-0.2ml(0.5-1.2mCi) of xenon in saline for 30min. The results are as follows. 1) In early erection phase, the half time(T1/2) and penile blood flow(Q) is 6.08min, 14.00ml/min/100g. It suggests that there is increased venous outflow in early erection phase. 2) In full erection phase, the T1/2 and Q is 34.15, 2.61. The venous outflow is nearly absent. 3) In detumescent phase, the T1/2 and Q is 1.50, 36.39. In summary, the penile xenon washout study is useful in studying the physiology of penile erection. Our results suggest that measurement in the flaccid state and stimulated erection with AVS are not useful for evaluation. The reliable results were obtained in a group of normal subjects erected with vasoactive agent.