One of the remarkable differences between human and porcine malignant hyperthermia (MH) is that MH in swine may be easily triggered by stress in awake animals but that human MH has generally been observed only during anesthesia. The report of Wingard and Gatz'of a higher incidence of unexplained deaths in susceptible families suggests that episodes of MH in awake humans may not be rare. These episodes might, however, be more subtle in humans than in swine, in that humans may learn to regulate their environment so as to restrict the initiating or contributing factors. The following case report of episodic hyperthermia may be an example of human MH triggering while awake.