[en] Analysis was performed on the relationships between the organ dose-equivalent rate due to natural background radiation (mSv/a) and three parameters of cancer risk: the age-adjusted cancer incidence (patients x 10⁵ persons x a^-1) in 13 large areas, the standardized mortality ratio of cancers in 46 large areas, and the cancer mortality in the population aged more than 40 years old (cancer deaths x 10⁵ persons x a^-1) in 649 small areas. The age-adjusted liver cancer incidence in males fitted the exponential model significantly (p<0.01) and the relationship of stomach cancer mortality of aged males in small areas fitted the linear model significantly (p<0.05). No relationship was observed with regard to female cancer in either case. The relationships between the three parameters and various other cancers of both sexes were not statistically significant. (author)