In medicine, priapism is defined as pathological state: a prolonged, generally painful erection not accompanied by sexual desire not ending with an ejaculation. Rare before 1980, priapism became more frequent after introduction of erection-inducing drugs by intracavernosal injections for treatment of impotence. Therefore, the medical practitioner can be faced with this problem, and the authors present with an algorithm the current diagnostic and therapeutic steps based on knowledge of pathology, physiopathology and etiology of this disease.