Stable metal microdispersions can be prepared using some polyelectrolytes such as quaternized poly(vinylpyridine). Microdispersions of Pd (Pd/PVP) were shown to be very effective catalysts for generation of hydrogen from formate or hypophosphite. The degree of dispersion and the activity of the catalysts were measured by the gas chromatography pulse technique. Comparison was made with commercially available heterogeneous Pd on carbon catalysts (Pd/C). Transmission electron microscopy measurements showed that the size of the Pd clusters, in the microdispersions, was of the order of 1 nm.