Aims Obesity is a risk factor for an acute coronary syndrome (ACS). The association between elevated body mass index (BMI) and ACS is independent of most traditional risk factors, suggesting a possible contribution of other body fat-related mediators. This study evaluated the association between adiponectin and ACS. Methods and results Four hundred and ninety-nine patients undergoing coronary angiography were divided into a subgroup without (n = 331) and with ACS (n = 168). In multiple regression analysis, higher adiponectin levels were independently associated with a lower risk of ACS [odds ratio (OR) = 0.61; 95% CIs: 0.46-0.81; P < 0.001]. In contrast, a higher BMI, a history of myocardial infarction, C-reactive protein, and angiographic coronary artery disease severity were all associated with a higher risk. The greatest increase in risk for ACS was seen at adiponectin levels <= 5.5 mu g/mL. Conclusion Higher plasma adiponectin levels are independently associated with a lower risk of ACS.