A review is given on the so-called electrochem. promotion (EP) denoting an elec. controlled modification of the activity and/or selectivity of a heterogeneous catalyst. Efficient EP in dispersed catalyst systems can be achieved using porous solid-electrolyte supports or by the manufg. of microstructured electrochem. reactors. The combustion of ethylene over IrO2 or RuO2 catalysts and the redn. of NO with propylene over Rh catalysts were chosen as model catalytic systems. The catalysts are all deposited on Y2O3-stabilized ZrO2 (YSZ) solid electrodes. First, a phenomenol. description of EP is given followed by a mechanistic interpretation and some theor. considerations. Then, fundamental studies on the above mentioned catalytic model systems are summarized. An electrochem. cell of the single-pellet type is applied, and cyclic voltammetry measurements are presented. For EP, 2 new cell designs were developed, a ring-shaped- and a multiple-channel configuration. [on SciFinder (R)]