BACKGROUND Studies of mortality in undetected coeliac disease compared with the general population give contradictory findings, suggesting it is either increased fourfold compared with the general population or not at all. AIM To establish all-cause and cause-specific mortality in undiagnosed coeliac disease, identified by anti-endomysial antibody (EMA) positivity, in the Cambridge GP Health Survey cohort. METHOD This cohort was recruited in 1990 from the general population aged 45-76 years. All deaths were ascertained from the Office for National Statistics. Mortality rates were calculated per 1000 person years and adjusted for age, gender, smoking and socioeconomic group using multivariate Cox regression to estimate hazard ratios (HR) and 95% confidence intervals (CI). RESULTS There were 117,914 patient years of follow-up (median 16.8 years) from 7527 participants. Eighty-seven had undetected coeliac disease, their all-cause mortality rate was 9.4 per 1000 person years (95% CI 5.4-16.1) compared with 12.7 (95% CI 12.1-13.4) in EMA-negative participants. The adjusted all-cause mortality HR was 0.98 (95% CI 0.57-1.69). Death due to cancer and circulatory diseases was not increased, adjusted HR were 1.27 (95% CI 0.57-2.85) and 1.39 (95% CI 0.66-2.92) respectively. CONCLUSIONS We observed no excess overall mortality in people aged over 45 years with undetected coeliac disease compared with the general population, nor any increase in deaths related to circulatory disease or cancer. Our findings do not support screening the general population aged over 45 years, for coeliac disease for the purpose of improving life expectancy.