The pharmacokinetic parameters of quinidine and quinine were determined and compared in seven mongrel dogs. Both drugs were given intravenously, with a minimum of 4 weeks between protocols, and blood samples collected for 20-24 h. Depending on the distribution phase, both two- and three-compartment models were used to describe the kinetics. The volumes of distribution, intercompartmental clearance rates, and volumes of the central and peripheral compartments were similar. The total body clearance (ClT) of quinidine, 3.58 ± 1.96 (SD) ml/kg/min, was 56% slower than that of quinine, 8.11 ± 3.03 ml/kg/min, with p < 0.02. Quinine half-life (t1/2), 6.58 ± 3.3 h, was 54% less than that of quinidine, 14.4 ± 4.10 h, p < 0.02.