The inhibitory effect of the overactivity of the sympathetic nervous system that results from outpatient clinical conditions leads to poor erectile response to intracavemous injection of papaverine. The effects of self manual genital stimulation for improvement of erectile quality in insufficient papaverine response were investigated in 171 impotent men. Twenty-nine (63.04%) of 46 patients who had a normal vascular system showed partial response to papaverine. Following self manual genital stimulation, full erection was achieved in all of them. Better erections were achieved in 28 of 42 patients with arterial disease. In patients subclassified as having slight, moderate, and severe arterial disease, improved erections were noted in 100%, 71.42%, and 64.28%, respectively. In the mixed vascular (arterial + venous) disease group (n = 46), the combined intracavernous injection of papaverine and stimulation (CIS) test led to a better erection in only 41.30%, whereas in the pure venogenic group (n = 37), this percentage was 66.66%. The inhibitory effect of the overactivity of the sympathetic nervous system is significantly reduced by the CIS test.