Anaesthetic requirements for nitrous oxide, enflurane and isoflurane were determined in mice selectively bred for their susceptibility (“long-sleep” mice) or resistance (“short-sleep” mice) to alcohol. Nitrous oxide and enflurane requirements, measured by the rolling-response test, were 34 and 20% greater, respectively, in short-sleep mice than in long-sleep mice. Although isoflurane requirement was 39% greater when measured by the tail-clamp test, it was not significantly different when measured by the rolling-response test. The greater anaesthetic requirement for short-sleep mice was not associated with a different synaptic membrane phospholipid, fatty acid or cholesterol composition.