• Malignant hyperthermia is an autosomal dominant disorder with variable expressivity that is caused by a membrane defect in the sarcolemma of myofibrils. A patient with strabismus (esotropia) had tachycardia and masseter muscle rigidity on exposure to succinylcholine chloride and halothane, but because of rapid recognition of the condition and discontinuation of the procedure, the potentially lethal complications of malignant hyperthermia did not develop. A serum creatine phosphokinase level showed a substantial increase above normal. Two weeks later, the patient underwent successful correction of the strabismus under general anesthesia, using morphine sulfate and thiopental sodium without complication. This condition is of interest to ophthalmologists because it occurs with increasing frequency in patients with strabismus and ptosis, and it may be triggered by certain local anesthetic agents often used by ophthalmologists.