We conducted a prospective study to determine the positive predictive value of papaverine testing to select patients in whom a vacuum constriction device would be a successful alternative to operative management of impotence. A total of 30 men presenting to an impotence clinic was evaluated with a series of papaverine dosages up to 60 mg. These patients then received a physician-administered trial of a vacuum constriction device, followed by 3 months of home use and a repeat objective evaluation. Initial responses to the device were poor, with 46% of the patients (14) achieving a rigid erection. However, after 3 months of home use 83% of the patients (25) achieved a rigid erection. The positive predictive value of a good response to the papaverine trial was 94%.