Cisplatin (DDP), a potent antineoplastic agent, is usually administered via a peripheral vein. Recently, there has been considerable interest in intraarterial regional infusions of DDP. The pharmacokinetics of DDP when administered by this technique have not been explored in detail. We studied DDP pharmacokinetics in dogs given DDP by infusion and bolus injection in the hepatic artery (H.A.), portal vein (portal V), and peripheral vein (P.V.). Blood and biliary platinum concentrations ([Pt]) were assayed by flameless atomic absorption spectrophotometry. During an infusion into the H.S., peak [Pt] in the vessel were markedly higher (mean value 19 micrograms/ml) than those found, simultaneously, in the portal V or superior vena cava. Following a bolus injection of DDP into the H.A., higher H.A. [Pt] were also seen, but [Pt] rapidly (within 5-10 minutes) equilibrated in all sites sampled. During the H.A. infusion, most [Pt] was in its free (active) form. Bile and hepatic tissue were also sampled. Hepatic artery infusions of DDP give high drug concentrations in the perfusing blood, while systemic [Pt] are much lower. During the infusion, the majority of DDP is in its active (unbound) state.