Twenty-four patients, treated after > or = 24 h of priapism caused by the injection of vasoactive drugs, were examined. The aetiology of impotence was psychogenic in > 50% of the patients (13/24). Most priapisms that lasted < 36 h could be treated successfully by puncture and alpha-adrenergic drugs without any fibrosis of the corpora cavernosa, and most patients continued to receive vasoactive agents for the treatment of impotence; but this approach was no longer adequate after priapism had lasted > = or 36 h when glandulocavernosal shunts were needed to achieve permanent detumescence. After > 48 h of priapism all the patients developed fibrosis of the corpora cavernosa and none of them was able to continue with the injections of vasoactive drugs. In addition to fibrosis of the penis, one fulminant infection, one case of urethral damage, one permanent shunt and two cases of transient hypertonia with ECG changes were seen. In order to save time, glandulocavernosal shunts should be performed without delay once priapism has lasted > 36 h.