The effects of intraperitoneal (IP) administration of chlordimeform (CDM) were investigated in 22-24 day old pentobarbital-anesthetized Sprague-Dawley rats. Animals (N=32) received a single IP injection of either 10, 30, or 60 mg/kg CDM, or normal saline vehicle. Heart rate (HR) and electrocardiogram (ECG) were monitored for all animals, while body temperature was maintained at control levels (37 deg C). HR decreased 21-29% in the treated animals and there were no differences observed across dose groups or over time. ECG effects were confined to rate-related changes only. The decrease in HR produced by CDM in these animals was comparable to the delayed HR effect seen in previous studies from this laboratory (Watkinson, 1985; Watkinson, 1986) despite major differences in dosing regimens and routes of administration.