The aim of this study was to develop an index that estimates late childhood obesity risk based on certain perinatal and family sociodemographic characteristics. The study was cross-sectional with retrospectively collected data from a representative sample of 2,294 primary schoolchildren, aged 9-13 years, in four counties from north, west, central, and south Greece. Mother's prepregnancy weight status, maternal smoking during pregnancy, maternal educational level, and infant weight gain in the first 6 months of life were combined with children's gender for the development of the Childhood Obesity Risk Evaluation (CORE) index. The score of the CORE index ranged from 0 to 11 units and each unit was associated with an obesity risk probability (range, 4-40 %). Cutoff point analysis revealed that a score ≤ 5 units best discriminated obese from non-obese children. On the basis of this cutoff point, the sensitivity of the CORE index was 54 % and the corresponding specificity 65 %.The proposed CORE index and the relevant percent risk probability chart could be used by pediatricians and other health professionals to identify children at high risk for obesity from early life. This simple and inexpensive tool could be useful in assisting early childhood obesity preventing initiatives.