Background: Increased plasma activity of gamma-glutamyltransferase (GGT) is associated with cardiovascular diseases (CVD) and mortality in the general population. We investigated the association between GGT, CVD and mortality in individuals with diabetes mellitus. Methods: Data used were from 1280 participants, aged 35-70years, with a confirmed diagnosis of diabetes mellitus in the European Prospective Investigation into Cancer and Nutrition in Potsdam (Germany), Bilthoven and Utrecht (the Netherlands). Multivariate hazard ratios (HR) and 95% confidence intervals (CI) for CVD (non-fatal and fatal events) and overall mortality were estimated using sex-specific quartiles of GGT. Results: After 8.2years follow-up, 108 incident CVD cases and 84 deaths were observed. Participants with high GGT activity had an increased mortality risk: HR in the highest quartile was 3.96 (95% CI 1.74, 9.00). This association was in particular present in former and current smokers, younger persons and those with a higher waist-height ratio and alcohol consumption. No associations were observed for non-fatal CVD and non-fatal and fatal CVD events combined. Conclusions: Higher GGT plasma activity is associated with increased all-cause mortality in individuals with diabetes.