In a 4-year 7-month-old boy with glucose-6-phosphate dehydrogenase deficiency and systemic arthritis a severe haemolytic anaemia occurred after the administration of acetylsalicylic acid. Erythrocyte fragmentation, with haemoglobin condensation zones next to clear zones, was observed on peripheral blood smears. Since viral or bacterial infections were excluded on the basis of the laboratory data, the anaemia was ascribed to aspirin.