Whether developmental periods exist in which children become particularly sensitive to environmental influences on eating is unclear. This research evaluated the effects of age on intake of large and self-selected portions among children 2 to 9 years of age. Seventy-five non-Hispanic white children 2 to 3, 5 to 6, and 8 to 9 years of age were seen at a dinner meal in reference, large, and self-selected portion size conditions in which the size of an entrée was age-appropriate, doubled, and determined by the child, respectively. Weighed food intake data were collected. Entrée bite size and bite frequency were assessed. Height and weight measurements were obtained. The effect of age on children's intake of the large portion was not significant. Entrée consumption was 29% greater (p < 0.001) and meal energy intake was 13% greater (p < 0.01) in the large portion condition than in the reference condition. Increases in entrée consumption were attributable to increases in average bite size (p < 0.001). Neither child weight nor maternal weight predicted children's intake of large portions. Self-selection resulted in decreased entrée (p < 0.05) and meal energy (p < 0.01) only among those children who ate more when served the large portion. The results of this research confirm that serving large entrée portions promotes increased intake at meals among 2- to 9-year-old children. These findings suggest that any age-related differences in children's response to large portions are likely to be smaller than previously suspected.