Kidneys from 42 infants were analysed for protein, fat, water, DNA and RNA. No significant differences in composition could be found between groups of children with different degrees of weight deficit. However, in a larger series of 200, it was shown that increasing degrees of weight deficit were associated with a reduction in kidney size. In the older children with the greatest degree of weight deficit, the kidney formed a significantly higher percentage of the body weight. The general conclusion is that in the most severely malnourished children kidneys are smaller than normal.