The cytotoixic effect of Pylorae Herba (Pyrola japonica Klenze) against L1210 and K-562 cells was studied in vitro. The methanolic extract of Pylorae Radix was add ed to the culture of L1210 cells and K-562 cells for the cytotoxic activity and the ED50 values of hexane, ethylacetate, buthanol and water fractions from methanolic extract were determined using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide) assay. The active constituent isolated by bioassay guided fractionation followed by purification gave rise to a yellow needle crystal and was clarified to be chimaphilline by the comparison with the published data. The average life spans with it were not prolonged significantly on tumor growth in hybrid female mouse (BDF1-KIST) inoculated subcutaneously with P388 cells.