PURPOSE: In spite of gastric cancer's decreasing incidence and mortality rates, it is still the most common cancer in Korea. In the present study, we examined the temporal trends of gastric cancer mortality during the past 20 years in Korea by using an age-period-cohort model, and we predicted the mortality rates for the next 10 years. MATERIALS AND METHODS: Data on the annual number of deaths due to gastric cancer and data on population statistics from 1984 to 2003 were obtained from the Korean National Statistical Office. A log-linear Poisson ageperiod-cohort model was used to estimate age, period and birth cohort effects. To project two periods (10 years) into the future, the new cohort values were estimated by performing linear regression that was applied to a chosen number of the most recent cohort values. RESULTS: The trends of gastric cancer mortality were predominantly explained by the cohort effect; the risk of gastric cancer death decreased since the 1919 birth cohort for both genders. The predicted, expected age-adjusted mortality rates per 100,000 for males and females are 45.72 and 23.75, respectively, during 2004~2008, and 34.62 and 17.93 respectively, during 2009~2013. During 2004~2008 and 2009~2013, the predicted numbers of deaths due to gastric cancer in males are 36,922 and 27,959, respectively, whereas those in females are 19,698 and 14,869, respectively. CONCLUSIONS: Not only the mortality, but also the incidence of gastric cancer in Korea is expected to further decrease in both men and women if the trends of the past 20 years continue.