The literature on the effects of protein-calorie supplementation on physical growth rates in height and weight is reviewed. Only studies carried out in moderately malnourished children from developing nations are considered. Two main questions are asked: 1) Do changes in protein-calorie intake cause changes in growth in these children, and 2) How does the impact on growth of supplemental foods vary with changing protein-calorie amounts of the supplement and of the home diet? Although, the experiments reviewed were shown to have a series of limitations, it was concluded that protein-calorie supplementation is causally related to growth. Moreover, the evidence reviewed suggests that the relative contribution of calories and proteins to the association depends upon which nutrient is limiting in the home diet. That is, if proteins are limiting, proteins and not calories are apparently beneficial for growth rates. On the other hand, if calories are limiting, calories alone seem to improve growth rates. This suggests that before expensive supplementation programs are instituted, one should first investigate which nutrients are most limiting in the home diet.