Deformability of erythrocytes of a patient with chronic nonspherocytic hemolytic anemia caused by a G-6-PD variant (G-6-PD Hamburg) in red cells was studied. The flow rate of erythrocytes from this patient through 5 μ m polycarbonate sieves was higher than that of red cells from healthy adults. Even under oxidative stress in vitro, the deformability of erythrocytes of the patient was only slightly decreased. The residual hemoglobin content of red cell membranes (ghosts) from this patient was lower than that of ghosts from healthy adults and of ghosts prepared from comparable reticulocyte-rich blood without G-6-PD deficiency. In contrast to the low enzymatic activity of G-6-PD Hamburg in the hemolysate, a high activity of this enzyme could be demonstrated in the ghosts from the patient. In view of the flexibility of this patient’s erythrocytes splenectomy is not to be recommended.