AIM:To evaluate the effects of Helicobacter pylor infection and other environmental factors on the development of gastric cancer.METHODS:A population-based case control study was conducted in Changle County, Fujian Province. The primary gastric cancer cases were histologically confirmed or diagnosed by surgery between January 1996 and March 1998. Healthy controls were randomly selected and matched by age, sex, and neighborhood of residence.A total of 101 pairs were included in the study. Specially trained interviewers conducted face-to-face interviews with the subjects according to a standardized questionnaire. Helicobacter pylori infections were measured by serum IgG antibody to Helicobacter pylori. Conditional Logistic Regression analysis was used.RESULTS:The presence of IgG antibody to Helicobacter pylori was 63.7% in study subjects, 56.0% in patients with cardiac cancer, and 60.5% in patients with non-cardiac gastric cancer. The risk factors of gastric cancer in Changle County were identified such as low educational level (OR = 3.864; 95% confidence interval (95%CI) 1.604-9.311), low consumption of fresh vegetables (OR = 4.925; 95%CI 1.356-17.885), high intake of fish sauce (OR = 10.587; 95%CI 2.821-39.738), unscheduled meals (OR = 4.254; 95%CI 1.445-12.552), and Helicobacter pylori infection (OR = 3.453; 95%CI 0.901-13.224).CONCLUSION:Helicobacter pylori infection may be important in the etiology of gastric cancer, but major risk factors other than Helicobacter pylori are responsible for the high gastric morbidity in Changle County.