Alkaloids have been isolated from a number of Litsea species (family Lauraceae) collected in New Guinea, and the major alkaloids and some minor alkaloids from several of these species have been identified. Other minor alkaloids have been detected by thin-layer chromatography in the crude alkaloids from all of the species examined. One Litsea species, identified as a previously undescribed species related to Litsea brassii 0. C. Schmidt and L. glutinosa (Lour.) C. B. Rob., is of special interest because extracts from the leaves have been shown to possess significant inhibitory activity against Sarcoma 180 in mice. This activity has been found to be associated with phenolic alkaloids isolated from the leaf, but the major alkaloid, laurotetanine (I), is inactive in the antitumour test. An incompletely purified minor constituent is considered to be reticuline (II). The presence of (I) and possibly (II) suggests that the antitumour-active compound could be related to the known tumour-inhibiting alkaloid thalicarpine, but comparison of the crude alkaloids with authentic thalicarpine by thin-layer chromatography shows that the leaf alkaloids do not contain thalicarpine. The alkaloids from the bark of this species have also been examined, and the major constituents identified as laurolitsine (III) and (+)-coclaurine (IV). Another Litsea species has been identified as Litsea glutinosa (Lour.) C. B. Rob. L. glutinosa is a wide-ranging species and is morphologically quite variable, and although the collections studied differ in some respects from L. brassii 0. C. Schmidt, which is regarded as a synonym of L. glutinosa, they all fall within the range of L. glutinosa. The leaf alkaloids of L. glutinosa have isoboldine (Va) and laurelliptine (Vb) as major components, and a minor base has been identified as the oxoaporphine alkaloid liriodenine (VI). Liriodenine has previously been obtained from a number of species belonging to the family Magnoliaceae, from Lysichiton camtschatcense in the family Araceae, and from Atherosperma moschatum (Monimiaceae). Laurotetanine (I) has also been shown to be present, but it was not obtained entirely free from laurelliptine. The bark alkaloids of L. glutinosa have not been examined in detail, but one major constituent has been identified as laurolitsine (III). The bark from Litsea solomonensis Nlen affords alkaloids in 0.03% yield, and the two major bases have been identified as laurolitsine (III) and (+)-reticuline (II). There is no significant amount of laurotetanine present in this species. The bark of another unidentified Litsea species, which can be designated only by the herbarium reference number TGH 12072, gives 0.53% alkaloids, with laurolitsine as the only major constituent. Laurotetanine has previously been isolated from Litsea chrysocoma, L. citrata, and L. cuheb and N-methyllaurotetanine from L. citrata.