The bulbs of Habranthus brachyandrus (Amaryllidaceae) have been extensively analyzed for their chemical constituents, resulting in the isolation of eight flavan derivatives (1-8), four of which are new naturally occurring compounds; a new hydroxybutyric acid glucoside (9); three known phenolic compounds (10-12); and six known alkaloids (13-18). The structures of the new compounds were determined on the basis of spectroscopic analysis, including two-dimensional (2D) NMR data, and chemical evidence. The isolated compounds and a few derivatives were evaluated for their cytotoxic activities against HL-60 human promyelocytic leukemia cells and HSC-2 human oral squamous cell carcinoma cells.