A technique is developed for the determination of the distribution of current density in operating fuel cells using a segmented cell structure concept. Real-time current density distribution data are presented and it is shown that they can contribute to an improved understanding of the reactant distribution over the active fuel cell area, for optimization of fuel cell performance. The technique also offers an alternative to a commercial polymer electrolyte membrane fuel cell stack in the small power range. When stacking several segmented structure electrodes, the resulting volume can be considerably reduced compared with a state-of-the-art stack.