An 11-year-old boy was given halothane, nitrous oxide and oxygen, pancuronium 0.4 mg and suxamethonium 100 mg for induction of anaesthesia. In response to this a marked jaw stiffness occurred which lasted for two minutes and the anaesthesia were terminated. Four hours of apnoea ensued and he suffered generalized severe myalgia lasting for one week. He was found to have atypical plasma cholinesterase with a dibucaine number of 12, indicating homozygocity. This was verified by study of the family. The case shows that prolonged jaw rigidity and myalgia may occur after suxamethonium in patients with atypical cholinesterase despite pretreatment with pancuronium.