The structures of laurifonine (17) (6,7,8,9-tetrahydro-2,3,12-trimethoxy-7-methyl-5H-dibenz[d,f]azonine), laurifine (18) (its 7-demethyl analogue), and laurifinine (19) (its 2-de-O-methyl analogue) have been established by chemical and spectroscopic studies. Cocculus laurifolius DC (Menispermaceae) has been a source of a variety of 1-benzyltetrahydroisoquinoline-derived alkaloids. Our interest in the alkaloids of C. laurifolius DC arose when hypotensive activity was observed in the 50% aqueous ethanolic extract of the leaves of the plant during a programme of screening of Indian plants over a wide range of biological activities. In further studies the hypotensive activity was concentrated in the alkaloid fraction. A search for the active principle(s) from this fraction resulted in the isolation of three new dibenz[d,f]azonine bases, laurifine, laurifonine, and laurifinine, assigned the structures (18), (17), and (19) respectively. The biogenesis of dibenz[d,f]azonine bases is discussed.