Malignant hyperthermia is a metabolic and genetic disease which present with multiple signs of variable intensity and time course. Most of signs are nonspecific to malignant hyperthermia an4 it is not unusual for malignant hyperthermia-susceptible patients to under- go their first anesthesia uneventfully. Thus,the accurate prediction of preanesthetic susceptibility and early diagnosis of malignant hyperthermis can be lifesaving. Recently, some episodes of signs and symptoms suggestive of malignant hyperthemia after spinal an- esthesia those were suspected to be malignant hyperthermia have been reported. In our hospital, two patients suffered from signs and symptoms suggestive of malignant hyperthermia after spinal anesthesia. One patient showed severe muscle rigidity on the un- blocked upper extremities and thorax, tachycardia (120-160beat/min) and hypertension (180-160/120-100mmHg) and later he showed high fever(38-40degrees C), generalized seizure and severe acidosis. He expired the next day of operation in spite of intensive care. The other patient showed shivering, high fever(39degrees C) and elevated serum CPK level(more than 1,500IU/ L) after spinal anesthesia. Intensive treatment with cooling was immediately initiated. Then, he recovered completely 6 hours later. His mother and a brother showed increased serum CPK level(91,112IU/L, respectively), too. Although we could not performed confirmatory diagnostic test, signs and symptoms were very similar to those of malignant hyperthermia. So, we suspected that it might be malignant hyperthermia.