Ellipticine, a plant alkaloid effective against murine leukemias and solid tumors, is presently undergoing toxicological assessment prior to clinical trial. A rapid, sensitive, reversed-phase high-performance liquid chromatographic method employing an internal standard was developed for the detection of ellipticine and its principal metabolite 9-hydroxyellipticine after extraction from biological samples. The method was successfully applied to the quantitation of ellipticine in mouse blood and tissues after intravenous administration of ellipticine and to mouse blood levels of drug after oral administration. Similar success was achieved in determinations of ellipticine and 9-hydroxyellipticine in samples of spiked human blood and plasma. Mouse blood ellipticine levels monitored over 3 h after the intravenous administration of drug demonstrated a biphasic decline with a terminal half-life of 52 min.