Two new N-methyltetrahydroprotoberberines, (-)-N-O-dimethylthaicanine [1] and (-)-N-methylthaicanine [2], were isolated from Anisocycla cymosa leaves together with four other known alkaloids: (-)-N-methyltetrahydropalmatine [3], anisocycline [4], palmatine [5], and stephenanthrine [6]. Their structures and stereochemistry were determined by chemical and spectrometric methods, including 2D NMR experiments (¹³C-¹H COSY and ¹H-¹H COSY). Anisocycla cymosa Troupin (Menispermaceae), a woody climber growing in Zaire, is used, according to the Zairian folkloric tradition, as a tonic, antipyretic, analgesic, and antirheumatic. We have previously identified in the roots several isoquinoline alkaloids: two protoberberines, anisocycline [4] and palmatine [5]; three bis-benzylisoquinolines, cocsoline, 1,2-dehydroapateine, and 1,2-dehydrotelobine; and one aporphine, remrefidine [2]. This paper details the isolation from A. cymosa leaves and the structure elucidation of two new N-methyltetrahydroprotoberberine alkaloids, (-)-N-O-dimethylthaicanine [1] and (-)-N-methylthaicanine [2], as well as the identification of four known alkaloids: three protoberberine alkaloids (-)-N-methyltetrahydropalmatine [3], anisocycline [4], and palmatine [5]; and one phenanthrene alkaloid, stephenanthrine [6].