In Japan, the age-adjusted mortalities of cancer of the stomach, uterus, liver (females only) and esophagus (females only) have been declining in recent years, whereas those of cancer of the lung, large intestine, pancreas, bile ducts, prostate and ovary have been increasing. The pattern of cancer among Japanese seems to be approaching that in Western countries. Although cancer screening and improvements of diagnostic and therapeutic techniques may have contributed to the changes in cancer mortality, the main reasons for these changes may be due to changes in environmental factors such as tobacco and diet. The mortalities of cancer of the stomach, bile ducts and liver are relatively high in Japan compared to those of foreign countries, while those of cancer of the breast, uterus, lung and colon are relatively low.