SUMMARY A 3-year-old child with severe tetanus, at the end of the third week of illness, developed circulatory arrest after suxamethonium injection. A similar incident also occurred in an adult patient with tetanus. Both incidents were attributable to acute hyperkalacmia induced by suxamethonium. In another patient with severe tetanus, after injection of suxamethonium 100 mg, the potassium level rose within 2 minutes from 3.8 m.equiv/l. to 7.4 m.equiv/l. Cardiac arrest followed suxamethonium injection also in two patients with uraemia. One further patient developed ventricular fibrillation when given suxa-methonium three weeks after a road accident in which he sustained multiple injuries. It is suggested that in these last three instances the increase of serum potassium caused by the injected suxamethonium was responsible for the circulatory arres
