BACKGROUND: Diabetes is a strong predictor of a poor outcome after coronary artery bypass grafting (CABG). The prevalence of prediabetes and its impact on the prognosis after CABG is not well described. In this study, we evaluated the prevalence and prognostic impact of the different states of abnormal glucose regulation (AGR) after CABG. PATIENTS AND METHODS: In this prospective study, we included 244 patients undergoing CABG. An oral glucose tolerance test was used to stratify patients into three groups: normoglycaemia, prediabetes and diabetes. The primary outcome was a composite of all-cause mortality and hospitalization for a nonfatal cardiovascular event. RESULTS: Among the patients, 86 (35%) were normoglycaemic and 58 (24%) had prediabetes; 100 (41%) patients had diabetes, of whom 28 (28%) had newly diagnosed diabetes on the basis of oral glucose tolerance test. During a mean follow-up period of 5.3 years, 25% of the study population suffered the primary outcome. There was a successive increase in the primary outcome rate from normoglycaemia through prediabetes to diabetes (adjusted hazard ratio 1.40; 95% confidence interval 1.01-1.96; P=0.045). CONCLUSION: With increasing severity of AGR, there is an increasing risk of new cardiovascular events after CABG. AGR is prevalent and predicts a poor outcome after CABG. Systematic screening for AGR seems reasonable to identify these high-risk patients.