Development of coronary collaterals (CCs) is triggered by the gradient between arteries due to obstruction and myocardial ischemia. Presence of CCs that feed the jeopardized myocardial area may limit the infarct size after coronary occlusion and may even provide a survival benefit. However, some patients develop good CCs, whereas others do not. The metabolic syndrome (MS) has been identified as a secondary target to decrease cardiovascular risk, although the effect of MS on development of CCs has not been investigated. We prospectively enrolled 596 consecutive patients (337 men and 259 women; mean age 56 +/- 8 years) who underwent coronary angiography at our center and were found to have total occlusion of the right coronary artery. Patients were then classified as having good CCs (Rentrop's grades 2 to 3) or poor CCs (Rentrop's grades 0 to 1). There were significant differences in terms of body mass index (kilograms of body weight divided by square meters of height), glucose levels, triglyceride levels, and years with angina pectoris between those with good and poor CCs. Prevalences of diabetes mellitus were 27.1% among patients with good CCs and 44% among those with poor CCs (p <0.001). Presence of MS was significantly higher in patients with poor CCs than in those with good CCs (78.4% vs 49.2%, p <0.001). In regression analysis, duration of angina pectoris (beta = 0.347, 95% confidence interval [CI] 0.266 to 0.453, p <0.001), presence of diabetes mellitus (beta = 1.829, 95% CI 1.021 to 3.279, p = 0.042), wall score (beta = 2.379, 95% CI 1.356 to 4.173, p = 0.003), and presence of MS (beta = 2.993, 95% CI 1.541 to 5.813, p = 0.001) were independent predictors of angiographically determined poor CCs. In conclusion, MS seems to be independently associated with poor CCs in patients with an occluded right coronary artery.