[en] The incidence of malignant tumors in the RERF Life Span Study (LSS) sample in Nagasaki as revealed by the Nagasaki Tumor Registry (Registry) has been investigated for the period 1959-78. No exposure status bias in data collection has been revealed. Neither method of diagnosis, reporting hospitals, nor the frequency of doubtful cases differ by exposure dose. Thus, the effect of a bias, if one exists, must be small and should not affect the interpretation of the results obtained in the present analysis. The risk of radiogenic cancer definitely increases with radiation dose for leukemia, cancer of the breast, lung, stomach, and thyroid, and suggestively so for cancer of the colon and urinary tract and multiple myeloma. However, there is no increase as yet for cancer of the esophagus, liver, gall bladder, uterus, ovary, and salivary gland, or for malignant lymphoma. For fatal cancers, these results strengthen those of the recent analysis of mortality based on death certificates on the same LSS cohort. In general, the relative risks based on incidence (that is, on Registry data) are either the same or slightly higher than those based on mortality for the same years; however, the absolute risk estimates (excess cancer per million person-year per rad) are far higher. (author)