The three medicinal herbs-Curcuman longa Linne, Paeonia japonica Miyabe, Scutellaria baikalensis George-irradiated with gamma rays were tested for their possible genotoxicity. The methanol-soluble and water-soluble fractions of the 10kGy gamma-irradiated herbs were examined in cultured Chinese hamster ovary(CHO) cells for their ability to induce micronuclei. No mutagenicity of each test material was detected in the assay with or without metabolic activation. The safety of the herbs irradiated with gamma rays at practical doses needs further investigations using in vivo genotoxicity and chronic and reproductive toxicity tests.