Abstract
1. The purpose of this paper is to propose the measurement of scalp hair diameter as a useful index of protein synthesis in the management of cases of malnutrition.2. Observations on scalp hair from ten control infants showed that each hair tapered very gradually towards its free end.3. Observations on scalp hair from twenty-six infants with kwashiorkor showed that each hair narrowed towards the follicle; the effect was statistically significant.4. After I month's treatment for kwashiorkor, scalp hair thickened towards the follicle and the effect was statistically significant.5. Serial measurements of the greatest diameter at 0·5 mm intervals along the hair shaft had a main trend which was related to nutritional history.6. The period of time over which narrowing of the hair shaft took place was calculated from the rate of hair growth and the serial diameter measurements: this time was always longer than the history of kwashiorkor.