Four patients developed penile erection when regional anaesthesia was induced with spinal block. In another patient, penile erection developed during fentanyl-induced general anaesthesia. Injection of metaraminol into corpus cavernosum successfully achieved detumescence in all these patients. The dose of metaraminol ranged from 10 to 25 micrograms, much less than that required for the treatment of vasodilator-induced priapism. Intracavernosal injection of metaraminol is a simple, effective and safe method for immediate relief of intraoperative penile erection. It is most useful when urogenital operation would be delayed by penile tumescence.