We investigated whether serum bilirubin level (a marker of heme oxygenase activity) is a predictor of high levels of SYNTAX score (SXscore) in patients with acute myocardial infarction. Patients (n = 281; male 77%; mean age 60±12) who were admitted with ST-elevation myocardial infarctions (STEMIs) were enrolled. Patients were divided into 2 groups. Group 1 was defined as SXscore <22 and group 2 was defined as SXscore ≥22. Total bilirubin levels were significantly higher in the high-SXscore group than in the low-SXscore group (0.86±0.42 vs 1.02±0.51, P = .005). A significant correlation was detected between total bilirubin and SXscore (r = .42; P = .001). At multivariate analysis, total bilirubin (odds ratio: 1.86, 95% confidence interval 1.04-3.35; P = .038) was an independent risk factor for high SXscore in patients with STEMI. In conclusion, serum bilirubin level is independently associated with SXscore in patients with STEMI.