Rats were implanted stereotaxically with permanent guide tubes aimed at the pontine reticular formation. Carbachol was microinjected in the awake, freely moving rats. Catalepsy was evaluated with the horizontal bar test. Intense and long-lasting, dose-dependent catalepsy was observed following microinjections of 2-8 micrograms of carbachol. Pretreatment with intraperitoneally administered scopolamine significantly reduced the cataleptogenic effect of carbachol. These results show that the pontine reticular formation is part of the neuroanatomical substrate of catalepsy induced by cholinergic drugs.