The aim of this paper was to evaluate the factors affecting body fat excess and distribution in prepubertal age.A cross-sectional survey was carried out on children attending the 4th grade of a primary school in Naples. Eighty-eight per cent of the total sample was examined: 52 girls, 58 boys; mean age = 9.6 yrs (s.e. +/- 0.10).Each child underwent a medical examination, anthropometric measurements and bio-impedance analysis of body composition. The parents were asked to fill in a questionnaire that included demographic data, family history, parent's weight and height, child's perinatal history and his or her involvement in sports activities. Data were analyzed by multiple linear regression. The results showed a direct correlation between parental BMI and children's anthropometric measurements: the children's BMI correlated with the fathers' (P = 0.02) and mothers' BMI(P = 0.027); the children's waist/hip ratio correlated with the fathers' BMI(P = 0.07); the children's subscapular skinfolds correlated with the father's (P = 0.07) and mothers' BMI(P = 0.02); the children's triceps skinfolds correlated with the fathers' BMI(P = 0.004). Among congenital factors, sex was shown to be correlated with the children's waist/hip ratio (P = 0.05) with a lower ratio in the female, indicating a sex influence on body fat distribution even in prepubertal age. The children's BMI correlated with their waist/hip ratio (P = 0.001). Children's systolic blood pressure showed a positive correlation with triceps (P = 0.04) and subscapular (P = 0.05) skinfolds thickness, % FAT-PLI (P = 0.02). No correlation was found between the children's BMI and their weight at birth, a family history of diabetes, hypertension, or hyperlipidemia. Among environmental factors, only the mother's weight gain during pregnancy (P = 0.03) and breast feeding (P = 0.05) showed a reverse correlation with the children's BMI.We foresee the importance of defining a series of factors associated with obesity in pediatric age in different populations. This field of investigation is intriguing because it could lead to a better understanding of the etiology of obesity and could help to establish preventive programs for this Western disease.