The asymmetric distribution of amino-containing phospholipids in plasma membranes is essential for the function and survival of mammalian cells. Phosphatidylserine (PS) is restricted to the inner leaflet of plasma membranes by an ATP-dependent transport process. Exposure of PS on the surface of cells serves as a binding site for haemostatic factors, triggers cell–cell interaction and recognition by macrophages and phospholipases. Exposure of PS on the red cell surface plays a significant role in sickle cell pathology. We report the identification of two different isoforms of the aminophospholipid translocase, Atp8a1, or flippase, in the murine red blood cell membrane.