Abstract In this paper, we provide an update on O 2-dependent membrane transport in red cells. O 2-sensitive membrane transport was compared in nucleated (chicken) and enucleated (human) red cells, to investigate effects on organic (glucose transporter [GLUT]) and inorganic (K +–Cl − cotransporter [KCC]/Na +–K +–2Cl − cotransporter [NKCC]) transporters, to study the response of so-called “housekeeping” transporters (Na +/K + pump and anion exchanger [AE]) and, finally, to compare O 2 sensitivity in normal human red cells with those from sickle cell patients. The Na +/K + pump showed no change in activity between oxygenated and deoxygenated cells in any of the samples. KCC in normal human red cells had the greatest O 2 sensitivity, being stimulated some 20-fold on oxygenation. It was more modestly stimulated by O 2 in chicken red cells and HbS cells. By contrast, NKCC was stimulated by deoxygenation in all cases. GLUT showed little response to O 2 tension, other than a small stimulation in deoxygenated chicken red cells. Finally, AE1 was stimulated by oxygenation in HbA cells, but this stimulation by O 2 was absent in HbS cells and pink ghosts prepared from HbA cells. The significance of these findings is discussed.