Abstract
1. Serial measurements of total body potassium were made in children while they were malnourished and as they recovered. Initially, there was a low total body potassium which rose slowly and reached the normal levels of 45 m-equiv./kg at 3–4 weeks after admission to hospital.2. The early stages of recovery were divided into three phases. In the first 5 days of treatment, retention of potassium served to correct a true potassium deficiency and the amount of potassium retained during this phase was related to the initial level of total body potassium. There was no relationship between serum potassium and total body potassium. There was indirect evidence that antecedent diarrhoea was an important factor in the production of potassium depletion.3. In the next phase—the lag phase—potassium was retained in relation to deposition of new body tissue.4. In the phase of rapid growth, potassium was also retained in the amount appropriate for deposition of new tissue.5. After the repair of the acute potassium depletion, potassium retention was always correlated with the protein intake.