BACKGROUND Intraoperative penile erections following the initiation of either regional or general anaesthesia is rare; however, when it occurs in patients undergoing urologic procedures it may delay, or even cancel the planned surgery. The aetiology is unclear. Various treatments proposed for producing detumescence are not always effective. Use of intracavernous alpha-adrenergic agonists is an efficient and rapid but short-lasting treatment. Furthermore, repeated intracavernous injections of vasoactive drugs may be harmful. Dexmedetomidine is a potent, selective α(2)-adrenoreceptor agonist. In our study, we evaluated the effect of dexmedetomidine on intraoperative penile erection. METHODS Penile erection developed during an endoscopic procedure in 12 more than 7,800 patients. Anaesthesia used was general in 3 patients, epidural in 1 patient and spinal in 8 patients. The erection rigidity was evaluated by the operating urologist. Dexmedetomidine was diluted in normal saline to a concentration of 4 μg/ml. In all of the cases, 0.5 μg/kg dexmedetomidine was injected intravenously. RESULTS The incidence of intraoperative penile erection was 0.34% for general anaesthesia, 0.11% spinal anaesthesia and 1.72% epidural anaesthesia at our institution. Detumescence was achieved in 9 patients during the first 5 min and in one patient at the 9th minute after a single intravenous dexmedetomidine (83%). There was no detumescence in two patients after 15 min (17%). CONCLUSIONS This study demonstrated that 0.5 μg/kg intravenous injection of dexmedetomidine is a simple, effective and safe method for immediate relief of intraoperative penile erection with high success rate.