We studied chromosome aberrations and survival in normal and dechorionated embryos of Misgurnus anguillicaudatus (Cobitidae, Pisces) exposed to mitomycin C (MMC) at concentrations of 25, 50 and 100μg/ml. The survival rates of dechorionated embryos exposed to MMC decreased dose-dependently but those of normal embryos exposed to 25 and 50μg/ml of MMC were not significantly different from the controls. On the other hand, the frequencies of chromosome aberrant cells in both normal and dechorionated embryos, which were observed in the blastula stage, increased dose-dependently. The frequencies in dechorionated embryos were not significantly higher in all doses than those in normal embryos. These results suggest that in normal embryos a large amount of MMC passed through the chorion and induced chromosome aberrations. For detecting chromosome aberrations, dechorionated embryos are more sensitive but normal embryos may also be sufficiently sensitive. The use of both normal and dechorionated embryos may give more detailed and useful information related to the properties of genotoxic chemicals. A chromosome aberration test using fish embryos showing a clear dose-response would be useful for monitoring genotoxic contaminants in the water environment.