Catalepsy is a state of behavioral immobility characterized by muscle rigidity and failure to correct an externally imposed posture for a prolonged period of time. Catalepsy is of important clinical relevance because of its similarity to behaviors seen in human disorders such as Parkinson’s disease and schizophrenia. Antipsychotic agents often increase catalepsy, thereby providing a measure of the extrapyramidal side-effects observed in humans exposed to chronic antipsychotics. In addition, catalepsy induced by the typical neuroleptic agent haloperidol in rodents can be used as a model of the extrapyramidal effects often seen in Parkinson’s Disease. Catalepsy is most commonly measured by the bar method and consists of placing an animal, after administration of a neuroleptic such as haloperidol, in a position with its front legs resting on a bar suspended above the floor of the test apparatus. Intensity of catalepsy is measured as the length of time the test subject maintains this abnormal posture.