Two new alkaloids, picrasidines M (II) and P (III), have been isolated from the root-bark of Picrasma quassioides BENNET. The structure of picrasidine L has been revised from 3-methyl-canthin-2, 6-dione to 3-methylcanthin-5, 6-dione (I). The structures were determined on the basis of spectral analysis and chemical evidence.