OBJECTIVE To evaluate serum leptin levels in obese Indian children and its correlation to anthropometric and biochemical parameters. METHODS Cohort study. METHODS Referral tertiary hospital. METHODS Leptin levels were measured in 36 children (26 boys, age 1.5 to 15 years) and 37 adults (21 men, age 25 to 69 years) with obesity and 29 normal weight controls (15 children and 14 adults). RESULTS Leptin levels were higher than controls in obese children (19.4 +/- 6.4 ng/mL against 5.4 +/- 1.7 ng/mL, p = 0.0001) and obese adults (18.9 +/- 6.4 ng/mL against 7.8 +/- 5.6 ng/mL, p = 0.0001). Leptin levels were higher than males in obese girls (23.5 +/- 1.7 ng/mL against 18.0 +/-7.6 ng/mL, p = 0.040) and women (21.3 +/- 4.4 ng/mL against 15.8 +/- 7.4 ng/mL). Leptin levels correlated with body mass index, waist circumference and waist to-hip ratio. A positive correlation was observed between serum leptin and cholesterol, triglycerides and LDL-cholesterol. No correlation was seen with fasting blood glucose and HDL-cholesterol. CONCLUSIONS Leptin levels correlate significantly with anthropometric and laboratory parameters in obese children. There is a need for further studies on the role of leptin in childhood obesity and metabolic syndrome.