Intracorporeal papaverine injections were performed for evaluation of penile erection on 120 patients with sexual impotence. This diagnostic technique was found to be simple, objective, realistic, and more precise in the differentiation of sexual dysfunction in men. In addition to observing the onset and duration of erection after papaverine injection, we could also classify the erectile rigidity by measuring the erectile angle while standing. The penile deformity after erection that possibly contributed to the etiology of patient's impotence could also easily be detected after papaverine injection. Thus we could differentiate 120 cases of impotence into the following types: psychogenic (26 cases), neurogenic (2 cases), mild vasculogenic (including physiologic) (33 cases), severe vasculogenic (54 cases) and pure venous leakage syndrome (5 cases). None of our patients developed fatal complications during or after the papaverine intracorporeal injection test; however, we experienced 5 cases of priapism requiring emergency management. Therefore, the injection must be done under the supervision of an experienced urologist.