'Anaesthetic erection' during transurethral surgery is dangerous and should be reversed before proceeding. Adequate anaesthesia should be ensured. Compression of the shaft penis and cooling with application of ice-cold swabs or ethyl chloride spray, should be tried in the first instance. If these measures fail, we propose intra-cavernosal injection of sympathomimetics as the first-line pharmacological treatment. Inform your anaesthetist. Use which ever drug you are most familiar with, or otherwise we recommend phenylephrine 0.2 mg. The administration of sympathomimetics can be supplemented with aspiration of 75 ml of cavernosal blood. A second dose of phenylephrine at 0.2 mg may be given with close monitoring for recurrent erection. If sympathomimetics fail, try penile block with plain lignocaine (10–20 ml of 1% solution). 'Anaesthetic erection' may be refractory to all pharmacological means. Intravenous glycopyrrolate deserves consideration in cardiovascularly high-risk patients or when the above treatments fail. Other novel invasive pharmacological treatments lack experience and should be resisted. Unresponsive erection is a very good reason for postponing endoscopic procedures.