In order to attest the evolutionary hypothesis of non-epithelialepithelial tumor shift (Okuyama and Mishina 1986), the published cancer incidence data for the population of Nagasaki City during the period of 1973-1977 was studied along with appropriate control populations of Fukuoka City, and Miyagi and Osaka prefectures. Significant increments of non-epithelial tumors including leukemias, and epithelial tumors such as cervical cancers and choriocarcinomas were observed. An inference was made to the post-atomic bomb radiation carcinogenesis that different organ systems responded to that irradiation with different oncogenic patterns : Neoplasms of the pre-vertebral organs (non-epithelial organ systems) were the first to react and tapered long (curve type I) ; Tumors of the vertebral but pre-mammalian (those of the digestive tract, respiratory and thyroid) could have formed two separate peaks, one for the early and high dosage and the other for the late and low dosage (II) ; With breast cancer or the mammalian symbol tumor, there was a single peak reflecting the cohort of reproductives (III). The evolutionary and phylogenetic progression could have taken place from I through III. Thus, cancer incidence analysis may be helpful in deciphering the atomic bomb radiation carcinogenesis. atomic bombing ; evolutionary concepts of cancer ; late cancer incidence ; radiation carcinogenesis When we examined the epidemiological aspects of cancer based on the published WHO data (Waterhous et al. 1982), there seemed to be a predominance of non-epithelial tumors during the period of infancy to adolescence, and that of epithelial ones thereafter (non-epithelial-epithelial tumor shift) (Okuyama and Mishina 1986). In the hope of obtaining an insight into the underlying evolutionary mechanisms, the epidemiological studies were expanded to include the population of Nagasaki City 30 years after the atomic bombing. In spite of probable dilution of the fraction of the atomic bomb survivors, the investigation was thought valid enough because the radiation is penetrating, and because carcinogenetic manifestation of radiation would take quite a long time. The results were thought to imply that the atomic bombing may possibly still have a hold on that victim population.