A total of 329 cases of gastric cancer from the Seoul Paik Hospital (1974-1987) were anlyzed with the Nakamuras formula to estimate its starting age. (1) Average age at the time of diagnosis 50.9 years old (male 51.1, female 50.7). This figure is 7 years younger and 14 years younger than those of Japanese and Americans, respectively. The differences can be speculated to be the same on the age differences of the cancer clcvcloprnent. Among these three countries. Generally, stronger the carcinogen, the age will become younger. (2) The estimated starting age of stomach cacner shows the highest in 40s age group, 30.7%, followed by 30s (26.1%), and 50s (20.4%). From 31 to 60 years, the figure is 77.2%. Average starting age is 42.5 years in both sex. (3) Interval between the starting age and the diagnosis (latent period) is 8.4 years in average (male 8.6, female 8.2). For the 41 EGC out of 329 stomach cancer, this latent period is 4 years. Therefore, the above 8.4 years will become ever closer to 4 years as early gastric cancer will he detected more in Korea in the future. (4) In coniparison with the age of EGC of Japan (1,300 cases), there are strikingly high percentages in the lower age groups is while low percentages in the upper age groups in Korea. This finding will indicate that Korean environment (traditional food) may cause the cancer more strongly than that of Japan.