Oriental herbal medicines were examined for mutagenicity in the reverse mutation test on Salmonella typimurium T A98/100 and chromosomal aberration test on cultured mammalian cells (Chinese hamster cell lines). The reverse mutation test was performed by a plate incorporation method with and without a metabolic activation system (S9 mix). The tested herbal medicines did not significantly increase revertible colonies on any of the test strains with and without a metabolic activation system (S9 mix) at concentrations of 1 mg/ml. In the chromosomal aberration test, most tested herbal medicines did not significantly increase the number of aberrant cells on any of the test strains with a metabolic activation system (S9 mix) at concentrations of 1 mg/ml, compared with the vehicle control. However. Ansu Semen significantly increased the number of aberrant cells without a metabolic activation system (S9 mix). Paeoniae Radix. Hoelen, Aurantii nobilis Pericarpium, Cnidii Rhizoma, Angeliacae gigantis Radix, Perillae Herba and Moutan Cortex Radicis slightly increased revertible colonies on any of the test strains with a metabolic activation system (S9 mix), These results indicate that most herbal medicines might be carefully used in obstetrics and gynecology, although they do not have the potent mutagenic potential under the present test conditions.