An electrochemical cell is designed and constructed to enable in situ measurements of the resistance of both the active mass and the interphase between the current-collector and the active mass in lead/acid test electrodes during cycling at well-defined degrees of compression ranging from zero to 90 kPa. Preliminary results of measurements on positive electrodes are well reproducible and show that, after conditioning cycles, both the interphase resistance and the active-mass resistance are independent of compression. Time changes of the two resistances are also studied and discussed.