SINCE 1966 approximately 20 case reports have appeared in medical literature which describe an abnormal reaction under anaesthesia characterized principally by muscle hypertonicity and hyperpyrexia, x-12 Usually these reactions have been associated with the use of succinylcholine. Two cases have occurred in our '250bed hospital within a nine-month period. They are presented here in an attempt to generate further interest in this most perplexing and lethal syndrome. Further research into this problem is urgently needed.