['To investigate the relation between ponderal index or birth weight and insulin resistance in late childhood.', 'An observational study of 92-term appropriate-for-gestational age infants was carried out. Weight and length were measured at birth and at 9 months and duration of breast feeding was noted at 9 months. Follow-up examinations at 10 years of age included measurement of weight, height, pubertal status, fasting insulin and glucose concentrations.', 'Ponderal index at birth was negatively (B±SE=-0.05±0.02; p=0.025) and current BMI was positively (B±SE=0.14±0.02; p<0.001) associated with insulin resistance measured as homeostasis model assessment (HOMA) at 10 years of age adjusted for gender and pubertal stage. Current BMI and ponderal index at birth were still significant after adjusting for weight at 9 months. Birth weight and weight at 9 months was not correlated with HOMA (p=0.58) adjusted for current BMI, gender and pubertal stage. HOMA was higher in the tertile with the lowest ponderal index than in the two remaining tertiles (p=0.024).'] Are thin newborns more insulin resistant at 10 years of age?