Rats were examined for the development of adverse motor and cognitive effects during and after 24 weeks of chronic haloperidol (HAL) administration using an 8-arm maze and a computerized apparatus for measuring spontaneous oral movements. In the maze, HAL caused a significant decline in choice accuracy only during the first week of administration, whereas it caused a significant decline in locomotor speed throughout drug administration. There were no effects of HAL on maze behavior after withdrawal. Haloperidol reduced the number of mouth movements during drug administration, but after withdrawal there was a significant increase. This replicated a previous finding from our lab. The oral movements which did occur in the HAL-treated rats were slower than normal. The timing of the HAL-induced cognitive dysfunction was similar to the Parkinson-like disorder shown by patients given chronic neuroleptics, whereas the timing of the increase in oral movements after the withdrawal of HAL was more related to the appearance of tardive dyskinesia. There was evidence in both tests of a persisting sedation during chronic neuroleptic administration.