Abstract: Objective To investigate the relationship between serum interleukin-10 (IL-10) level and insulin resistance (IR) in patients with metabolic syndrome (MS). Methods Eighteen MS subjects and 18 age-matched normal subjects were enrolled. IR was evaluated by hyperinsulinemic-euglycemic clamp technique and serum IL-10 level measured by ELISA. Pearson’s correlation analysis was used to investigate the relationship between serum IL-10 level and IR. Results Serum IL-10 levels were significantly higher in patients with MS than in the controls [1.3 (0.8/3.1) pg/ml vs 2.4 (1.1/4.5) pg/ml, P<0.05], and glucose metabolic rate (M value) derived from hyperinsulinemic-euglycemic clamp technique was lower in MS subjects than in controls [(5.76±1.81) mg/kg·min vs (8.39±1.25) mg/kg·min], P<0.05]. Serum IL-10 levels showed a positive correlation with M value (P<0.05). Conclusion Patients with MS have greater IR and lower serum IL-10 levels than normal subjects, and lowered IL-10 levels might be involved in the pathogenesis of IR in MS.