An outbreak of paralytic shellfish poisoning occurred in southern Taiwan, affecting 116 persons who had consumed purple clams. Two victims died within four hours. Gonyautoxins were identified as causative toxins. During the outbreak, five patients with paralytic shellfish poisoning were seen in our hospital. All recovered following supportive treatments. Serum creatine kinase concentration was elevated in three of the five patients. The levels of the enzyme did not seem to correlate with the severity of poisoning. The most significant finding was the previously unreported observation of elevation of the creatine kinase MB level. In all four patients who had creatine kinase MB value determined, it was elevated.