1. The present study was conducted to evaluate the cytotoxic effects of Coptis chinensis and Epimedium sagittatum extracts and their major constituents on hepatoma and leukaemia cells in vitro. 2. Four human liver cancer cell lines, namely HepG2, Hep3B, SK-Hep1 and PLC/PRF/5, and four leukaemia cell lines, namely K562, U937, P3H1 and Raji, were used in the present study. 3. Of the two crude drugs, C. chinensis exhibited the strongest activity against SK-Hep1 (IC50 = 7 microg/mL) and Raji (IC50 = 4 microg/mL) cell lines. The IC50 values for C. chinensis on HepG2, Hep3B and PLC/PRF/5 cell lines were 20, 55 and 35 microg/mL, respectively. The IC50 values for C. chinensis on K562, U937 and P3H1 cell lines were 29, 29 and 31 microg/mL, respectively. 4. With the exception of HepG2 and Hep3B, the E. sagittatum extract inhibited the proliferation of all cell lines (SK-Hep1, PLC/PRF/5, K562, U937, P3H1 and Raji), with IC50 values of 15, 57, 74, 221, 40 and 80 microg/mL, respectively. 5. Interestingly, the two major compounds of C. chinensis, berberine and coptisine, showed a strong inhibition on the proliferation of both hepatoma and leukaemia cell lines, with IC50 values varying from 1.4 to 15.2 microg/mL and from 0.6 to 14.1 microg/mL, respectively. However, icariin (the major compound of E. sagittatum) showed no inhibition of either the hepatoma or leukaemia cell lines. 6. The results of the present study suggest that the C. chinensis extract and its major constituents berberine and coptisine possess active antihepatoma and antileukaemia activities.