A 6-year-old boy with chronic haemolytic anaemia was found to have glucose 6-phosphate dehydrogenase (G6PD) deficiency and the morphological, ultrastructural and serological features of congenital dyserythropoietic anaemia (CDA) type II. The patient's mother was heterozygous for G6PD deficiency. G6PD from the patient's red cells, upon partial purification and full characterization, was found to be a new variant designated G6PD Gabrovizza. We conclude that two distinct genetic abnormalities coexisted in this patient. We suggest that CDA type II may become clinically more expressed when another abnormality of the erythrocytes coexists.