Agranulocytosis developed in a 20-year-old Greek patient with beta-thalassaemia major, 11 weeks after commencing chelation with the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) and 6 weeks after receiving the drug at a total daily dose of 105 mg/kg. The patient presented with generalised weakness, low-grade fever and sore throat. The total white cell count was 2.0 x 10(9)/l with 0.1 x 10(9)/l neutrophils. The patient was admitted to hospital and successfully treated with intravenous broad-spectrum antibiotics. Neutrophil count recovered 7 weeks later. A number of immunological tests were performed in an attempt to elucidate the cause of agranulocytosis. These investigations gave inconclusive evidence for the presence of a weak IgM antibody to myeloid cells exposed to L1 in this patient. Further studies are required, however, to evaluate the mechanism in any other patient who develops agranulocytosis in association with L1 therapy.