The significance of the metabolic syndrome in type 1 diabetes is not well understood. This study aimed to estimate its prevalence and attendant complications. Four hundred twenty-seven type 1 diabetic subjects were grouped according to the presence or absence of metabolic syndrome (WHO criteria). Macro- and microvascular complications were compared between the groups as individual and as composite endpoints. Data were analyzed for the total cohort and in subgroups according to duration of diabetes quartiles (<6.9, 7-12.9, 13-19.9, and >20 years) and year of presentation. Fifteen percent of individuals fulfilled the WHO criteria for metabolic syndrome, and of these, 26.9% were insulin resistant, as compared with 3.4% of those without metabolic syndrome [odds ratio (OR)=8.9, P=.001]. Both BMI and metabolic syndrome showed an increasing trend from 1992 to 2003. Those with metabolic syndrome required significantly higher insulin dosage [0.9 (0.7-1.2) vs. 0.6 (0.5-0.9) units/kg, P=.03], were older [35.0 (26.2-47.3) vs. 29.7 (23.4-36.4) years, P=.002], and had longer duration of diabetes [19.7 (10.7-25.6) vs. 12.1 (6.3-17.9) years, P=.0001]. They also had a significantly higher macrovascular composite endpoint (OR=3.3, P=.02) as well as higher macrovascular and microvascular composite endpoint (OR=3.1, P=.0001). The prevalence of stroke (OR=22.8, P=.008), peripheral vascular disease (OR=7.3, P=.05), and severe retinopathy (OR=3.7, P=.01) is higher in subjects with metabolic syndrome in the >or=20-year quartile group; in addition, these subjects have higher macrovascular composite endpoint (OR=3.9, P=.03) and macrovascular and microvascular composite endpoint (OR=2.9, P=.03). This remained so even when subjects with albuminuria were excluded. Some individuals with type 1 diabetes can also have metabolic syndrome. They are more prone to complications and require even more intensive glycemic control and reduction of macrovascular risk factors.