Objective: To investigate the cytotoxic effect of ethanol extract of the stem bark of asam kandis [Garcinia cowa Roxb. (G. cowa)] on T47D breast cancer cell line. Methods: The cytotoxicity of ethanol extract was carried out against human breast cancer cell line (T47D) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. The extract was added at various concentrations (0.1, 1, 10 and 100 μg/mL). The level of cytotoxicity was determined by calculating the level of IC