Apart from their stability in various operating conditions, the two main properties of ion-exchange membranes (IEMs) are the conductivity and selectivity, but both are difficult to obtain simultaneously at high values. This presentation deals with different ways of measurements, including specific characterization such as electrochemical impedance spectroscopy, Raman vibrational spectroscopy and radiotracers. Different transport models to reach fundamental transport parameters are also presented. Two cases of structure correlations will illustrate this topic: a cation-exchange membrane in strong basic solutions and a high-proton-conducting membrane based on sulfonated polyimide polymers.