Extra-large portions served at restaurants put consumers at risk of overweight and obesity, including children. Developing standards for portions sizes for kids' menus could reduce the risk that children will be served more food than they need for normal growth. We reviewed the calorie content of foods offered on kids' menus at franchised restaurants and US Department of Agriculture published recipes for use in schools. Using an expert panel, we developed recommendations for portion sizes for different food categories at restaurants that would reduce the likelihood that children would be served too much when they dine out. We found that portions of a la carte items offered on kids' menus averaged 147% more calories than the portions recommended by the panel, with hundreds of single servings exceeding 600 calories, the amount recommended as a maximum for an entire children's meal. Expert panel members recommended that single servings of entrees not exceed 300 calories, fried potatoes not exceed 100 calories, and desserts not exceed 150 calories on kids' menus. Restaurants should revise their portions for children and downsize them to match with recommendations that will reduce the risk that children will be served too much. The current kid's menu offerings are likely to be partly responsible for childhood obesity. New guidelines offer reasonable benchmarks for food service to children.