Pharmacokinetic modeling has suggested, and clinical investigations have confirmed, that intracavitary drug administration can result in a much greater drug exposure for the cavity into which the agent is instilled compared to the plasma. Both the safety and the efficacy of several agents administered individually or in combination have now been demonstrated. Several malignancies, in particular ovarian carcinoma and malignant mesothelioma, which remain confined to body cavities for much of their natural history, might be most rationally treated by the intracavitary treatment approach. Early clinical trials have demonstrated significant activity of intracavitary chemotherapy in both of these malignancies. Optimal drugs and dosages as well as appropriate scheduling for the various tumors involving body cavities remain to be defined. Whether or not combination intracavitary chemotherapy will significantly improve survival of patients with malignant disease confined to body cavities must await carefully controlled clinical trials comparing this treatment approach to standard systemically administered chemotherapy.