Some of the rats used in an experiment on survival seemed to die for no apparent reason. Some wild rats died when simply held in the hand, others when placed in water, and more as a result of both procedures. All died when their whiskers were trimmed. Few tame rats were killed by these procedures. Richter at first erroneously supposed that Cannon's hypothesis [see preceding abstract] explained the deaths. The true cause was probably parasympathetic hyperactivity, which perhaps is promoted in man by hopelessness; this is a possible explanation of 'voodoo death'.