With the use of flameless atomic absorption spectrophotometry, we have devised a technique for measuring zinc in neutrophils. Neutrophil zinc levels in patients with sickle cell anemia correlated significantly with height and weight, and with serum testosterone in men. Such correlations were not seen with zinc levels in plasma or erythrocytes. We also report the beneficial effects of zinc supplementation on longitudinal growth and body weight in 14- to 18-year-old patients with sickle cell anemia. Thus, the neutrophil zinc level is a reliable and sensitive indicator of zinc deficiency in these patients.