A simultaneous study of the modification of red blood cell deformability by the filtration technique on a micropore filter, and of the parameters describing the electrochemical impedance associated with ferrocyanide anion [Fe(CN)6]4− oxidation at a rotating disc electrode, leads to the proposition of a relation which linkds deformability to the product of charge-transfer resistance by the stationary current intensity (Rt I). This allows us to connect the evolution of the mechanical resistance of red blood cells in the course of ageing during their conservation in the blood bank, with modifications of the product Rt I.