Chlordecone (Kepone) given in the diet at 10 and 30 ppm for 90 days to adult male Fischer 344 rats produced significant behavioral changes. Rats were tested in a battery of behavioral screening tests for sensorimotor functions at 30, 60, and 90 days of dosing, and 30 days postdosing. Body weight loss was significant by 90 days of dosing with 30 ppm chlordecone; no weight change was seen at the lower dose. Variable effects on grip strength were seen during and after dosing. The magnitude of startle responsiveness to an air puff stimulus was significantly increased by 30 days of dosing in the 30 ppm dose group. Both 10 and 30 ppm doses produced increased responsiveness to an acoustic stimulus by 60 days of dosing. Negative geotaxis and tail flick response to thermal stimulation did not change. By 30 days postdosing, significant behavioral alterations still persisted in startle responsiveness.