The effect of cooking, including washing in running water and heating, on the removal of toxicity from pufferfish liver was investigated. Twenty-one samples of poisonous liver with toxicity levels from 61MU/g to 1, 270MU/g were examined by a cooking method which is one of those used in the professional pufferfish stores in Oita prefecture. The toxicity was reduced to less than 5MU/g and the detoxication profiles during the cooking process were similar in all cases. Nevertheless, it still seems desirable to examine more toxic pufferfish liver than those used in this experiment, and other cooking methods.