To estimate the penile blood flow changes during artificial with erection intracorporeal papaverine injection, we injected 99 m Technitium-Human Serum Albumin via antecubital vein simultaneously and calculate the radioisotope activity of the penis using computerized Gamma Camera. We classified the results into 3 groups according to the transit time, erection persistent time and venous index in 67 impotence patients. We defined the arteriogenic impotence with the delayed transit time (more than 600 seconds) in 13 patients and venogenic with the shortened erection persistant time (less than 200 seconds) and decreased venous index (less than 0.8) in 11 patients. The rest of them (43 patients) were regarded as equivocal impotence, probably nonvasculogenic or psychogenic.