Abstract Outbred Wistar rats were selectively bred for predisposition to catalepsy for 16 generations. The rats predisposed to catalepsy are characterized by an increased (in an unselected control population) or decreased (in S 13) motor activity, decreased defecation scores, and elevated blood pressure. Selective breeding for catalepsy for 16 generations resulted in the production of a stock with about 50% of the animals showing a consistent cataleptic reaction, versus about 10% in the control unselected stock. From segregation analysis it was concluded that predisposition to catalepsy is inherited as an oligogenic dominant characteristic with incomplete penetrance. The same seems to be the case with predisposition to pendulum movements. There is a positive phenotypical and genetic relationship between predisposition to catalepsy and predisposition to pendulum movements, and a negative relationship between predisposition to catalepsy and incidence of audiogenic seizures. A genetic model for the relationship between catalepsy, pendulum movements and audiogenic epilepsy is proposed.