We studied the Syrian hamster embryo (SHE) cell transformation by focus assay for detecting the carcinogenicity of chrysotile asbestos fibers collected from Sichuan Xinkang Asbestos Mine and particulate coal dusts from Jiayang Coal Mine. Both these mines belong to Sichuan Province. Results showed that transformed foci were found in the methylcholanthrene group and in the two asbestos dosing groups (8 micrograms/ml and 4 micrograms/ml), whereas no transformed foci were noted in the coal dust groups and no spontaneous transformation in the negative control groups. Morphologically, the transformed foci were documented by light and electronmicroscopy. Significant differences between the positive transformed groups and the negative control groups were demonstrated by statistic analysis. The results indicate that Sichuan Xinkang chrysotile asbestos fibers are of carcinogenic potentiality, and Jiayang coal dusts do not induce transformation in SHE cells.