["To assess maternal perceptions of children's current and ideal body sizes, and the meaning of and factors contributing to overweight in infancy and early childhood among Mexican-origin mothers living in Mexico and in California.", 'A quali-quantitative study combining focus groups and a self-administered questionnaire.', 'A purposive sample of 84 low-income, Mexican-origin mothers of 4- to 6-year-old children recruited between March 2006 and January 2008 from rural and urban communities in Mexico and California.', "Bivariate, multivariate, and qualitative analyses of maternal perceptions of children's actual and ideal body size supplemented by qualitative analyses of meaning of and factors contributing to childhood overweight/obesity.", "Ideal child body size was considerably lower among Mexican-origin mothers living in California (3.86+/-0.56) than it was among mothers living in Mexico (4.32+/-0.83), and this difference was significant (P=0.001) after adjusting for sociodemographic covariates. Among mothers of overweight children, 82% of mothers in California were dissatisfied with their child's weight compared with 29% of mothers in Mexico (P=0.003). Focus-group results suggest that these differences in the perception of children's ideal body size can be attributable to differences in body size norms among mothers and awareness of the negative effects of obesity that occur after migration to California."] Do maternal perceptions of early childhood ideal body weight differ among Mexican-origin mothers residing in Mexico compared to California?