AIM: To determine the risk of malignancy and mortality in patients with a positive endomysial or anti-gliadin an- tibody test in Northern Ireland. METHODS: A population-based retrospective cohort study design was used. Laboratory test results used in the diagnosis of coeliac disease were obtained from the Regional Immunology Laboratory, cancer statistics from the Northern Ireland Cancer Registry and mortal- ity statistics from the General Registrar Office, Northern Ireland. Age standardized incidence ratios of malignant neoplasms and standardized mortality ratios of all-cause and cause-specific mortality were calculated. RESULTS: A total of 13 338 people had an endomysial antibody and/or an anti-gliadin antibody test in Northern Ireland between 1993 and 1996. There were 490 pa- tients who tested positive for endomysial antibodies and they were assumed to have coeliac disease. There were 1133 patients who tested positive for anti-gliadin anti- bodies and they were defined as gluten sensitive. Ma- lignant neoplasms were not significantly associated with coeliac disease; however, all-cause mortality was signifi- cantly increased following diagnosis. The standardized incidence and mortality ratios for non-Hodgkin’s lym- phoma were increased in coeliac disease patients but did not reach statistical significance. Lung and breast cancer incidence were significantly lower and all-cause mortal-ity, mortality from malignant neoplasms, non-Hodgkin’s lymphoma and digestive system disorders were signifi- cantly higher in gluten sensitive patients compared to the Northern Ireland population. CONCLUSION: Patients with coeliac disease or gluten sensitivity had higher mortality rates than the Northern Ireland population. This association persists more than one year after diagnosis in patients testing positive for anti-gliadin antibodies. Breast cancer is significantly re- duced in the cohort of patients with gluten sensitivity. AIM: To determine the risk of malignancy and mortality in patients with a positive endomysial or anti-gliadin an-tibody test in Northern Ireland. METHODS: A population-based retrospective cohort study design was used. Laboratory test results used in the diagnosis of coeliac disease were obtained from the Regional Immunology Laboratory, cancer statistics from the Northern Ireland Cancer Registry and Mortal- ity statistics from the General Registrar Office, Northern Ireland. Age NER at birth mater neoplasms and standardized mortality ratios of all-cause and cause-specific RESULTS were A total of 13 338 people had an endomysial antibody and / or an anti-gliadin antibody test in Northern Ireland between 1993 and 1996. There were 490 pa tients who tested positive for endomysial antibodies and they were checked to have coeliac disease. There were 1133 patients who tested positive for anti-gliadin anti- bodies and they were defined as gluten sens however, all-cause mortality was signifi- cantly increased following the diagnosis. The standardized incidence and mortality ratios for non-Hodgkin’s lym-phoma were increased in coeliac disease patients but did not reach statistical significance. Lung and breast cancer incidence were significantly lower and all-cause mortal-ity, mortality from malignant neoplasms, non-Hodgkin’s lymphoma and digestive system disorders were signifi- cantly higher in gluten sensitive patients compared to the Northern Ireland population. CONCLUSION : Patients with coeliac disease or gluten sensitivity had higher mortality rates than the Northern Ireland population. This association persists more than one year after diagnosis in patients testing positive for anti-gliadin antibodies. Breast cancer is significantly re- duced in the cohort of patients with gluten sensitivity.