Hexafluorenium was used to potentiate suxamethonium in 93 patients undergoing abdominal surgery of up to 60 minutes duration. Anaesthesia consisted of thiopentone-nitrous oxide-oxygen, usually with pethidine supplementation, and ventilation was controlled. In one group hexafluorenium was administered before induction, the intubating dose of suxamethonium then providing relaxation for surgery. In a second group of patients hexafluorenium followed by suxamethonium was given after the intubating dose of suxamethonium had worn off. No bronchospasm or cardiovascular side effects were noted. It is considered that this drug combination provides excellent relaxation for abdominal surgery but is particularly suitable in cases which last 30 minutes or longer.