The nitrogen metabolism of 43 children admitted to the hospital with kwashiorkor has been investigated during the early and convalescent phases of recovery by means of 168 nitrogen balance studies. These observations have been supplemented by clinical assessment, including weight gain and serial estimations of serum albumin. Milk diets were used as a standard for comparison with diets in which maize meal was the sole source of protein. The effects of supplementation of maize meal with glycine, or with pea flour with or without maize germ have been evaluated. With milk diets nitrogen retention was significantly higher in the first 2 weeks of treatment than after that time. The better retentions of the earlier phase of treatment take place in the presence of impaired absorption of nitrogen from the gastrointestinal tract. These findings indicate that degree of protein depletion is an important variable in the interpretation of nitrogen balance in the early recovery phase of kwashiorkor. Nitrogen retention with pure maize meal diets was significantly less than that resulting from an equicaloric and equinitrogenous milk diet. With maize diets during convalescence, concentration of serum albumin decreases and weight gain is less consistent than with milk diets. Maize meal is not improved by a supplement of glycine. While absorption of nitrogen (as a percentage of nitrogen intake) from maize diets is less than from milk diets, the data also indicate less efficient tissue utilisation of nitrogen from maize protein. Supplementation of maize with pea flour, (Pisum sativum) with or without maize germ, resulted in significant improvement of nitrogen retention. These supplemented maize diets are capable of curing mild cases of kwashiorkor and maintaining a satisfactory concentration of serum albumin and weight gain for as long as 150 days. It is concluded that while these simple vegetable mixtures are not as efficient sources of protein as diets containing milk, they are effective in maintaining nitrogen retention and growth under metabolic ward conditions. They may therefore prove of value in the prevention of kwashiorkor.