BACKGROUNDGastric cancer remains a leading cause of cancer death worldwide. In Taiwan, gastric cancer is the sixth leading cause of cancer mortality in both males and females.AIMTo evaluate secular trends in gastric cancer incidence according to age, sex, and Helicobacter pylori (H. pylori) treatment in Taiwan.METHODSIn this population-based study, we used the national Taiwan Cancer Registry database. Annual percent changes in incidence rates were used to describe secular trends in incidence rates and sex ratios of gastric cancer in Taiwan. Pearsonâs product-moment correlation coefficients were used to analyze the correlation between annual age-adjusted incidence rates and the annual number of patients treated with antibiotic therapy for H. pylori infection.RESULTSThe annual percent changes showed continuously decreasing rates of gastric cancer among both males and females. However, the decreasing trends differed by sex, with an annual percent change of -2.58% in males and -2.14% in females. The age-specific incidence rates increased with age. Within the same age group, more recent time periods showed lower incidence rates than greater time periods. Similarly, the sex ratio was lower in later birth cohorts than in earlier birth cohorts. Age-adjusted incidence rates substantially decreased with increasing numbers of patients being treated with antibiotic therapy for H. pylori infection during 2005 to 2016 (r = 0.72).CONCLUSIONWe observed steadily decreasing trends with differential sex ratios in the incidence of gastric cancer in Taiwan. These results support H. pylori eradication programs in Taiwan.