Increased body mass index (BMI), a parameter of total body fat content, is associated with an increased mortality in the general population. However, recent studies have shown a paradoxic relation between BMI and mortality in specific patient populations. This study investigated the association of BMI with long-term mortality in patients with known or suspected coronary artery disease. In a retrospective cohort study of 5,950 patients (mean age 61 +/- 13 years; 67% men), BMI, cardiovascular risk markers (age, gender, hypertension, diabetes, current smoking, angina pectoris, old myocardial infarction, heart failure, hypercholesterolemia, and previous coronary revascularization), and outcome were noted. The patient population was categorized as underweight, normal, overweight, and obese based on BMI according to the World Health Organization classification. Mean follow-up time was 6 +/- 2.6 years. Incidences of long-term mortality in underweight, normal, overweight, and obese were 39%, 35%, 24%, and 20%, respectively. In a multivariate analysis model, the hazard ratio (HR) for mortality in underweight patients was 2.4 (95% confidence interval [CI] 1.7 to 3.7). Overweight and obese patients had a significantly lower mortality than patients with a normal BMI (HR 0.65, 95% CI 0.6 to 0.7, for overweight; HR 0.61, 95% CI 0.5 to 0.7, for obese patients). In conclusion, BMI is inversely related to long-term mortality in patients with known or suspected coronary artery disease. A lower BMI was an independent predictor of long-term mortality, whereas an improved outcome was observed in overweight and obese patients.