Heart rate (HR) and body temperature (TEMP) were monitored in unanesthetized, unrestrained adult rats following intraperitoneal administration of 0, 10, 30, or 60 mg/kg of the pesticide chlordimeform (CDM). Although significant decreases were observed in both HR and TEMP in all treated groups, the HR response was of a lesser magnitude than that which was reported in previous studies from this laboratory using anesthetized animals. The attenuation of the toxic response seen in the present study may be casually related to the observed decrease in TEMP.