A rapid, sensitive and simple method was developed for the quantitation of the plasma concentration of N4-[2,6-dimethoxy-4-methyl-5-[(3-trifluoromethyl)phenoxy]-8- quinolinyl]-1,4-pentanediamine, a new antimalarial active against Plasmodium vivax. N4-(5-Hexoxy-6-methoxy-4-methyl-8-quinolinyl)-1,4- pentanediamine diphosphate, a similar 8-aminoquinoline, was used as an internal standard. The method involves sample clean-up by a prepacked cyano solid-phase column followed by reversed-phase liquid chromatography and oxidative electrochemical detection at +0.95 V. The assay has been validated to 5 ng/ml of plasma and is sensitive to 1 ng/ml of plasma. The results of a pilot study assessing the relative oral bioavailability of two different salt forms of the new antimalarial in dogs show the usefulness of the method for animal and human pharmacokinetic studies.