Objective: To examine the variability of food portions served and consumed by African-American and Hispanic-American pre-school children attending Head Start. Design: Cross-sectional. Setting: Food consumption by pre-schoolers (n 796) enrolled in sixteen Head Start centres in Houston, Texas (51% boys, 42% African-American, mean age 4 years) were assessed during 3 d of lunch meals using digital photography. Descriptive statistics and multilevel regression models, adjusting for classroom and school clustering effects, were determined. Subjects: Head Start pre-schoolers aged 3-5 years. Results: Mean amount served was 2428 kJ (580 kcal) and 572 g. Mean intake was 1421 kJ (339 kcal) and 331 g: 20% protein, 46% carbohydrate and 34% fat. Plate waste was 43% (range: 38% (fruit) to 61% (vegetables)). Mean CV of food served was 29 %: 33% for entrees, 44% for vegetables, 60% for fruit and 76% for starches. Mean CV of food consumed was 46 %: 58% for entrees, 86% for fruit, 96% for vegetables and 111% for starches. Total gram amount of food served was positively correlated with consumption (r=0.43, P0.001). Conclusions: Plate waste and variation in amounts served and consumed were substantial; amounts served were associated with amounts consumed. Large portion sizes may contribute to paediatric obesity by promoting excessive intake at meals. Understanding factors influencing portion sizes provides insight about specific intervention strategies that can be used in obesity prevention programmes. (author abstract)