Erection is a rare event during lower urinary tract surgery. When it is extremely refractory, endoscopy is impossible and the lower urinary tract surgery may need to be deferred. The development of erection during spinal anaesthesia is due to manipulations before complete installation of sensory block or incomplete blockade of sacral segments (S2 to S4) supplying the nervi erigentes. The mechanism of erection during general anaesthesia remains poorly elucidated. General anaesthesia may suppress central or peripheral sympathetic control of flaccidity. The peripheral target could be the smooth muscle of the cavernous tissue, either by a direct action or via alpha-adrenergic receptors. Psychogenic and reflexogenic stimuli have also been proposed, possibly facilitated by amplification of sensations during stage II anaesthesia. The various treatments are based on experience acquired in the field of priapism. Systemic treatments such as ketamine an beta 2 mimetics or benzodiazepines are not always effective and are associated with considerable adverse effects. Intracavernous injections of alpha-adrenergic drugs constitute the treatment of choice. Phenylephrine and etilefrine are preferred because of their rapid efficacy and particularly their only moderate cardiovascular adverse effects.