Objective: To assess the association between exclusive breast-feeding and childhood overweight. Design: Cross-sectional data are from the baseline survey of the longitudinal cohort study IDEFICS. Exclusive rather than partial breast-feeding is the focus of the study due to the theoretical relationship between exclusive breast-feeding and development of dietary self-regulation. Children's measured heights and weights were used to calculate weight status, while waist-to-height ratio (WtHR) and skinfold measures were examined as alternative indicators of adiposity and fat patterning. Setting: Examination centres in eight European countries (Italy, Estonia, Cyprus, Belgium, Sweden, Hungary, Germany and Spain). Subjects: The analysis included 14 726 children aged 2-9 years for whom early feeding practices were reported by parents in standardized questionnaires. Results: After controlling for education, income and other potential confounders, breast-feeding exclusively for 4-6 months was protective of overweight (including obesity) when compared with children never exclusively breast-fed (OR=0.73; 95% CI 0.63, 0.85) across all measures of overweight. Exclusively breast-feeding for 6 months offered slightly more protection than for 4 and 5 months combined (OR=0.71; 95% CI 0.58, 0.85). The associations could not be explained by socio-economic characteristics or maternal overweight. Conclusions: This multi-country investigation indicated that exclusive breast-feeding for 4-6 months may confer protection against overweight in addition to other known benefits. There was no demonstrated benefit of exclusive breast-feeding for more than 6 months or combination feeding for any duration across all measures of overweight examined.