Background/ AIMS: H. pylori infection is undoubtedly an important risk factor for gastric cancer. It remains unclear, however, whether antibiotic treatment may prevent gastric cancer development. Our aim was to assess long-term gastric cancer risks in historic cohorts of patients presumed to have been heavily exposed to antibiotics. SUBJECTS: Using the Swedish Inpatient Register, we identified 501,757 individuals discharged with any of ten selected infectious disease diagnoses between 1970 and 2003. METHODS: We counted person-time and non-cardia gastric cancer occurrences through linkage to virtually complete population and health care registers. Standardized incidence ratios (SIRs) were calculated for comparisons with cancer incidence rates of the general population in Sweden. RESULTS: No reduction in gastric cancer risk was observed in the infectious disease cohort in total (SIR=1.08, 95% confidence intervals [CIs]=1.00-1.17), or for any of the presumed antibiotic regimens. There were no clear trends towards decreasing risk with time of follow-up, but the risk tended to fall with increasing age at first hospitalization for the infection (p