Chlorpromazine-induced depression of rectal temperatures in rabbits kept at 20 degrees was used to determine relative biophasic drug levels corresponding to observed hypothermic response intensities, which then served to establish a triexponential linear mathematical model describing drug transference and drug action in this system. Comparisons of various experimentally known, slow intravenous infusion drug inputs of chlorpromazine with drug inputs computed by deconvolution, using the derived model and observed temperature depressions, served to verify the accuracy of the model for the 0.50-4.0 mg/kg dosage range.