Tuberculosis (TB) is a widespread infectious disease.It remains an enormous public health problem and global challenge.It was estimated that there were 9.27 million individuals with TB in 2007, representing 139 per 100 000 person-years (py).Malnutrition, deterioration of immunity due to local or systemic effects of cancer itself and the administration of chemo-or radiotherapy are likely to play an important role in TB infection or reactivation.Several hospital-based studies have reported that patients with lung, head and neck and haematological cancers are prone to TB infection.The relationship between gastric cancer and TB has rarely been investigated.In a retrospective cohort study from 2000 to2006, data for 2215 patients diagnosed with gastric cancer at were compared with data from the Centers for Disease Control, Taiwan.In patients with gastric cancer without a history of gastrectomy and without previous anti-TB treatment, the overall crude incidence of new-onset TB was 788 per 100,000 py.Compared with the general population, the overall age-sex standardized incidence was 134.3 per 100,000 py.The recurrence rate among patients with previous anti-TB treatment was 18% (4/22) after gastric cancer diagnosis.Gastrectomy was a significant risk factor for active TB incidence.Multivariate analysis showed old age, male gender, previous anti-TB treatment, and gastrectomy as significant risk factors for TB.In stratified analysis, an interaction between old TB patterns on chest films and chemotherapy was observed.We concluded that old age, male gender, previous anti-TB treatment, and gastrectomy were significant risk factors for TB in gastric cancer patients.An increased TB reactivation after chemotherapy was observed in gastric cancer patients with old TB pattern chest films initially, suggesting an interaction between chest film patterns and chemotherapy.