Thirty-one alkaloids have been isolated from the leaves and from the stem bark of Alstonia angustifolia from Malaysia. Twenty of them were known compounds: yohimbine, 0-acetyl yohimbine, pleiocarpamine, fluorocarpamine, cathafoline, cabucraline, N-l desmethylquaternine, vincamajine, normacusine B, lochnerine, affinisine, akuammicine, ll-methoxyakuammicine, antirhine, alstonisine, alstonerine, alstophylline, macralstonine, villalstonine and tetrahydrocantleyine. Among the 11 novel alkaloids, three were monomers: 19,20-dehydro-lo-methoxytalcarpine, 19,20-dehydro-0-acetyl yohimbine and hydroxystrictamine, and eight were dimers: villalstonine N-4'-oxide, lomethoxy villalstonine, lo-methoxyvillalstonine N-4'-oxide, lO-methoxymacrocarpamine, lo-methoxymacrocarpamine N-4'-oxide, angusticraline, alstocraline and foliacraline. Structural elucidation of the new alkaloids was based on spectral data analysis including high field 'H and 13CNMR.