Background People with metabolic syndrome are at higher risk for developing coronary artery disease (CAD). The effect of the metabolic syndrome on outcomes in patients with preexisting CAD has not been well studied. This study was conducted to assess the prevalence, characteristics, in hospital and long term prognosis of CAD with metabolic syndrome and to determine the factors influencing the prognosis of the disease. Methods The DESIRE registry contains data of 3696 patients with CAD between 2001 and 2004. Mean long term followup was (829±373) days. Diagnosis of metabolic syndrome was based on modified International Diabetes Federation (IDF) Worldwide Definition of the Metabolic Syndrome,using body mass index (BMI) instead of waist circumference. Results Of 2596 patients with complete records of height, weight, and so on, 1280 (49.3%) were identified with metabolic syndrome. The patients with metabolic syndrome had higher level of body mass index, systolic blood pressure, diastolic blood pressure, fasting glucose and disordered blood lipid (all P<0.0001), with higher creatinine [(10.5±4.3) mg/L vs (9.9±2.9) mg/L, P<0.0001] and the number of white blood cells [(7.49±2.86) ×109/L vs (7.19±2.62) ×109/L, P=0.008) compared with those without metabolic syndrome. The patients with metabolic syndrome showed severer coronary angiographic alterations (left main artery and/or ≥2-vessel) (73.6% vs 69.6%, P=0.031). There were no significant differences of major adverse cardiac and cerebral events (MACCE) or mortality in hospital between the two groups. During followup, the ratio of MACCE in CAD with metabolic syndrome patients increased significantly (11.8% vs 10.0%, P=0.044). Fasting blood glucose (≥1000 mg/L) and triglyceride (TG, ≥1500 mg/L) were responsible for most of the increased risk associated with the metabolic syndrome (adjusted OR 1.465, 95% CI 1.037-1.874, P=0.032; OR 1.378, 95% CI 1.014-1.768, P=0.044). Conclusions The prevalence of metabolic syndrome was very high in CAD patients. The metabolic syndrome confers a higher risk of long term MACCE in patients with CAD, and dysglycaemia and hypertriglycaemia appear to be responsible for most of the associated risk. Background People with metabolic syndrome are at higher risk for developing coronary artery disease (CAD). The effect of the metabolic syndrome on outcomes in patients with preexisting CAD has not been well studied. This study was conducted to assess the prevalence, characteristics, in hospital and long term prognosis of CAD with metabolic syndrome and to determine the factors influencing the prognosis of the disease. Methods The DESIRE registry contains data of 3696 patients with CAD between 2001 and 2004. Mean long term followup was (829 ± 373) days. Diagnosis of metabolic syndrome was based on modified International Diabetes Federation (IDF) Worldwide Definition of the Metabolic Syndrome, using body mass index (BMI) instead of waist circumference. Results Of 2596 patients with complete records of height, weight, and so on, 1280 ( 49.3%) were identified with metabolic syndrome. The patients with metabolic syndrome had higher level of body mass index, systolic blood pressure, diastolic b lood pressure, fasting glucose and disordered blood lipid (all P <0.0001), with higher creatinine [(10.5 ± 4.3) mg / L vs (9.9 ± 2.9) mg / (7.49 ± 2.86) × 109 / L vs (7.19 ± 2.62) × 109 / L, P = 0.008) compared with those without metabolic syndrome. The patients with metabolic syndrome showed severer coronary angiographic alterations (left main artery and / or ≥2 -vessel) (73.6% vs 69.6%, P = 0.031). There were no significant differences of major adverse cardiac and cerebral events (MACCE) or mortality in hospitals between the two groups. During followup, the ratio of MACCE in CAD with metabolic Fasting blood glucose (≥1000 mg / L) and triglyceride (TG, ≥1500 mg / L) were responsible for most of the increased risk associated with the metabolic syndrome (11.8% vs 10.0%, P = 0.044) (adjusted OR 1.465, 95% CI 1.037-1.874, P = 0.032; OR 1.378, 95% CI 1.014-1.768, P = 0.044) Conclusions The prevalence of metabolic syndrome was very high in CAD patients. The metabolic syndrome confers a higher risk of long term MACCE in patients with CAD, and dysglycaemia and hypertriglycaemia appear to be responsible for most of the associated risk.