It is well known that rats maintained on a thiamine deficient diet exhibit significant weight loss, decrease in heart frequency, behavioral disorders such as circling movements, muricide aggression as well as symptoms of polyneuritis. After a series of pharmacological studies on thiamine deficient rats, I reported that the actions of certain drugs affecting the central nervous system were modified by acute thiamine deficiency in animals. In brief, thiamine deficiency increased sensitivity to the hypnotic action of barbiturates and reduced the cataleptic action by tetrabenazine4). I am planning to investigate the effect of analgesics (morphine, pentazocine, aspirin……) on thiamine deficient animals, since little is known about changes in the pain threshold following severe thiamine deficiency. In this study, an attempt was made to investigate the changes in the pain threshold of rats as a consequence of thiamine deficiency.