OBJECTIVE: Infants with higher adiposity at birth may be at greater risk of developing obesity later in life. IGF-1 is important for intrauterine growth and may be a useful early life marker of adiposity, and thus later obesity risk. The aim of this study was to determine the relationship between cord blood IGF-1, neonatal anthropometrics and markers of neonatal adiposity. DESIGN, PATIENTS AND MEASUREMENTS: A cross-sectional study design was utilized to study a multiethnic cohort of full-term neonates born to healthy mothers with normal glucose tolerance at a large university hospital. Neonatal cord blood was collected after birth and assayed for IGF-1, leptin and C-peptide. Neonatal body composition was measured between 24 and 72 h of life using the method of air displacement plethysmography. RESULTS: Cord blood IGF-1 was positively and significantly associated with markers of neonatal adiposity in models adjusted for maternal age at delivery, race, maternal prepregnancy BMI, gestational age at delivery and neonatal sex: birthweight (r = 0.62, P < 0.001), leptin (r = 0.33, P = 0.018), fat mass (r = 0.52, P < 0.001) and percent body fat (r = 0.51, P < 0.001). Cord blood IGF-1 was not associated with cord blood C-peptide. CONCLUSIONS: Cord blood IGF-1 is strongly associated with all measures of neonatal adiposity suggesting that IGF-1 may be an important contributor to in utero neonatal fat accumulation.