To explain the peculiarities shown by the codeposition of inert particles from electrolytic baths, a mechanism based on two successive adsorption steps is proposed. In the first step the particles are loosely adsorbed, and they are in equilibrium with the particles in suspension. In the second step the particles are irreversibly adsorbed. Making a few elementary hypotheses about the mechanism that governs the two steps it is possible to deduce a general expression relating the concentration of the embedded particles to the suspension concentration and the electrode overpotential. This relationship is verified experimentally.