Background. Approximately 26% of 2- to 5-year olds in the United States are overweight (body mass index [BMI] > 85th %ile for age and sex). Overweight preschool-aged children are more than four times as likely to become obese adults compared to their normal weight counterparts, placing them at high risk for cardiovascular disease (CVD) onset. Little is known about the perinatal etiology of early childhood obesity by ethnicity. We explored these relationships among US 3- to 6-year olds. Methods. Representative samples (1999-2004) of the National Health and Nutrition Examination Survey (NHANES) were used to examine the association between overweight, mother’s smoking status during pregnancy, birthweight, and infant feeding method. (N=1,481). Results. Mexican American children were significantly more likely than their counterparts to be obese (P <0.001). Chi square analysis showed that breastfeeding had a modest protective effect against BMI > 95th%ile for Hispanics (p<0.05). Mexican American and non-Hispanic black mothers who smoked during pregnancy were significantly more likely to have an obese preschool child than their non-smoking counterparts (P<0.01, P<0.05, respectively). Logistic regression analysis showed a protective effect for both mother quitting smoking during pregnancy (OR 0.74, 95% CI, 0.58, 0.95) and normal birthweight (OR 0.53, 95% CI, 0.30, 0.93) for obesity. Conclusions. Obesity in children as young as preschool age is associated with perinatal factors. Minority women should not smoke and should be encouraged to breastfeed as their children are disproportionately affected by the obesity epidemic, which in turn is a risk factor for later life onset of CVD.