In order to investigate the safety of a water extract (ADP) of 1 : 1 mixture of Anemarrhena rhizoma and Phellodendron cortex for alleviating benign prostate hyperplasia, genotoxicity studies in bacterial and mammalian cell assay systems, namely, the Ames bacterial reverse mutation and chromosomal aberration assays were performed. As shown by the results of the Ames bacterial reversion assay, ADP in the range of 625-5000 $mu extrm{g}$/plate did not induce mutagenicity in Salmonella typhimurium TA 98, TA 100, TA 1535 and TA 1537 strains in the absence or in the presence of S9 (the microsomal fraction of rat liver homogenate) metabolic activation. The $IC_{50}$ (50% cell growth inhibition concentration) values of ADP for the chromosomal aberration assay were determined; these were 2425 $mu extrm{g}$/ml in the absence and 8126 $mu extrm{g}$/ml in the presence of S9 metabolic activation in Chinese hamster lung (CHL) fibroblast cell culture. No chromosomal aberration was observed in CHL cells treated with ADP at 2425, 1212.5 and 606.25 $mu extrm{g}$/ml in the absence, or at 8126, 4063 and 2031.5 $mu extrm{g}$/ml in the presence of S9 metabolic activation. These results show that under the conditions used, ADP does not harmfully affect the bacterial or mammalian cell system at the gene level.