1. The plasma copper and iron levels, the hematocrit and hemoglobin concentration and the total plasma protein concentration were significantly lower in patients with kwashiorkor than in controls of the same age group.
2. There was a significant diminution in total circulating copper in the kwashiorkor patients.
3. Paraphenylene diamine oxidase activity was lower in the patients with kwashiorkor than in controls, indicating that there is a diminution in the level of the active group of ceruloplasmin which contains copper.
4. Whether the low plasma copper found is due to dietary deficiency, to malabsorption of copper, or whether it is secondary to inadequate protein intake is discussed.