Zinc determinations were made in a 5 month-old female with the Chediak-Higashi syndrome. Zinc concentrations in plasma, erythrocytes, lymphocytes and granulocytes from the patient were significantly higher than those in healthy children of a similar age, and were higher than--or equal to--those of healthy adults. Lymphocyte zinc levels in the parents were significantly lower than those of healthy adults. Although the cause of the high zinc concentrations in these samples cannot be fully explained , abnormally high zinc levels may be partially responsible for impairment of some leukocyte functions in patients with CHS since zinc plays a central role in cellular metabolism.