We present the first case of priapism following radical prostatectomy. A 66-year-old man with normal erections underwent radical retropubic prostatectomy with unilateral nerve sparing. Pathology showed a pT2c pN0 Gleason score 3 + 3 = 6 prostate cancer and the postoperative course was uneventful. Ten days after surgery he recognized a spontaneous painful penile erection without sexual stimulation which occurred in a standing position and disappeared in a supine position. These episodes recurred several times during the next 3 weeks and then completely vanished. Pathophysiologically, we postulate intermittent position-depending venous obstruction due to local hematoma or thrombosis.