It is said that stable strontium (Sr), which exists naturally in living cells as a microelement, has cytoprotective effects on liver cells in mammals. We attempted to examine the cytoprotective and anticancer effects of Sr using the rat carcinogenetic model induced by DMH (1,2-dimethylhydrazine). In a comparison of animals given UFT, PSK and Sr or UFT and PSK, carcinogenes in the colon and also increases in immunosuppressive acidic protein (IAP) levels were suppressed. Electron microscopic observation in the Sr group revealed a tendency toward stabilization of the mitochondrial membrane and highly developed rough endoplasmic reticulum in both the right and left lobe. This tendency became more obvious as the duration of oral intake of Sr was prolonged. Our study suggest that the cytoprotective effect of Sr on mitochondria in the liver may suppress carcinogenesis.