Ten patients with nutritional copper deficiency were studied in terms of neutrophil counts and anti-neutrophil antibodies (ANA). In four patients with severe or moderate copper deficiency, the production of ANA was positive and two patients with a severe deficiency had neutropenia. After copper supplementation, ANA titres became negative or were reduced in all patients and neutrophil counts reverted to normal in two patients. It thus appears that copper deficiency is linked to the production of ANA, a condition which partly responsible for neutropenia.