Three patients with Leigh's syndrome developed respiratory failure following general anesthesia. Although all three had respiratory symptoms prior to the anesthetic, the diagnosis was not suspected at the time of the procedure in two of the children. We reviewed the case notes of 16 other patients with Leigh's syndrome. Eight had received anesthetic agents without incident. Although the majority subsequently developed respiratory abnormalities and died with respiratory failure, this problem was not evident at the time of anesthesia. In the presence of respiratory abnormalities, general anesthesia carries significant risks in Leigh's syndrome.