Three experiments were performed using rats to determine if hyperthermia. when given after training on a one-trial passive avoidance task. could serve as an amnesic agent. In comparison to controls frequently used in the amnesia paradigm. the results of Experiment 1 indicated that hyperthermia produced severe amnesia. Results from Experiments 2a and 2b indicated that there was a direct relationship between severity of hyperthermia and degree of amnesia. Furthermore. it appeared that hyperthermia produced amnesia without the concomitant decrease in temperature that has been seen with other amnesic agents such as electroconvulsive shock and hypothermia. The results of Experiment 3 indicated that the effectiveness of hyperthermia as an amnesic agent diminished as the temporal interval between the learned event and the induction of hyperthermia increased. These results indicated that. on empirical grounds. the memory loss produced by hyperthermia resembled that produced by such other amnesic agents as ECS and hypothermia.