To determine whether age of bottle-weaning is associated with overweight in young children, National Health and Nutrition Examination Survey III data for 3027 children aged 3-5 years were analyzed. The main outcome measure, the child's body mass index (BMI), was measured as: <85%, 85-95%, >95%. Mean bottle-weaning age was 18.78 months. After adjustment for potential confounders, each additional month of bottle use corresponded to a 3% increase in the odds of being in a higher BMI category (95% CI 0.0099-0.0535). Prolonged bottle use in young children is associated with increased risk of overweight. From a preventive medicine standpoint, decreasing exposure to this potential risk for childhood overweight is indicated.