The differential effects of intravenous (IV) intraperitoneal (IP) administration of chlordimeform (CDM) were investigated in 22-30 day old pentobarbital-anesthetized Sprague-Dawley rats. The first group of animals (N=25) were given sequential IV injections of 5, 10, 30, 60, and 120 mg/kg CDM, or normal saline vehicle followed by a single injection of 60 mg/kg CDM. Heart rate (HR), arterial blood pressure (BP), and electrocardiogram (ECG) were monitored for all animals. CDM produced profound acute effects on all cardiovascular parameters monitored and persistent delayed effects on HR and BP. These effects were similar to but less severe than those observed in a previous study using geriatric animals. The second group of animals (N=32) received a single IP injection of either 10, 30, or 60 mg/kg CDM, or normal saline vehicle. The decrease in HR produced by CDM in these animals was comparable to the delayed HR effect seen in the first group despite the differences in dosing regimens and routes of administration.