A fit 36-year-old parturient received a general anaesthetic for manual removal of a retained placenta. She underwent rapid sequence induction of anaesthesia with suxamethonium, shortly followed by 10 mg of mivacurium. One hour later she had failed to establish adequate ventilation despite administration of drugs to reverse neuromuscular blockade. A provisional diagnosis of suxamethonium-related apnoea was made and her lungs were ventilated overnight on the Intensive Care Unit. Plasma cholinesterase levels at the time were reduced to one-third of normal, with normal dibucaine and fluoride numbers. One month later her levels were back within the reference range.