In a 61-year-old man with glucose-6-phosphate dehydrogenase (G6PD) deficiency and poorly controlled non-insulin-dependent diabetes mellitus, an episode of acute haemolysis occurred after the administration of glyburide (glibenclamide). Erythrocyte fragmentation, with haemoglobin condensation zones next to clear zones, was observed on peripheral blood smears. Since autoimmune haemolysis was excluded on the basis of laboratory data, acute haemolysis was ascribed to G6PD deficiency.