We have isolated a number of alkaloids from ethyl acetate extracts of the leaves of Mitragyna javanica, Koord. and Valeton and Mitragyna hirsuta, Havil. The chemical constitution of two and possibly three new alkaloids is now presented. The extracts of Mitragyna javanica yielded ajmalicine, mitraphylline, isomitraphylline, Pa 7 [which may be identical with vineridine (Kasymov, Yuldashev & Yunusov, 1965a,b)] and mitrajavine, together with a yellow alkaloid. The extracts of Mitragyna hirsuta yielded mitraphylline, isomitraphylline, rhynchophylline, isorhynchophylline and hirsutine. Mitraphylline, isomitraphylline, rhynchophylline, isorhynchophylline and ajmalicine were identified by comparison of the m.p., mixed m.p., [α]D, Rf values (thin layer chromatography), ultraviolet and infrared spectra of the isolated and authentic samples of these alkaloids. Pa 7 is an oxindole alkaloid of a methoxymitraphylline type with the aromatic methoxy group in the 11 position, and may be identical to vineridine. Mitrajavine is an indole alkaloid of a methoxy-ajmalicine type (9-OMe) with a cis C2H orientation and a molecule of water of hydration. Hirsutine is an indole alkaloid of the corynantheidine-type with an ethyl group.