The number of electrolyte/metal/pore three-phase boundaries in the SOFC anode cermet was determined in a cross-section photo according to the intercepted-segment method and given as the volume concentration of the electrochemically active phase boundary. The apparent geometrical exchange current density of hydrogen oxidation served as a relativizing measure of electrochemical activity. A direct correlation was found between the number of optically visible three-phase boundaries of ＇electrolyte/nickel agglomerates/gas pores＇ in the unit volume of the electrode and the apparent electrochemical exchange current density. The electrode was also analysed porosimetrically by a standard porosimetry method (MSP) and the porosimetric curves were compared with the optical/electrochemical measurements of the same electrode. This comparison revealed that the sum of the integrated volume of nickel agglomerates and the single nickel particles in contact with the electrolyte give the total amount of the active nickel volume whose surface is directly proportional to the amount of optically visible three-phase boundaries in the unit volume.