In this article, we analyze the performance of a dluted catalyst pellet consisting of inert and active particles under diffusion influenced conditions and pore-mouth poisoning. First, we establish the requirements for validty of the analytical soltuions of the diluted pellet equations. Secondly, we show that, under pore-mouth poisoning conditions, a diluted pellet can display considerably longer lifetimes than a uniformly impregnated catalyst. Conversely, for the same lifetime, use of a diluted pellet can result in savings of the catalytic agent. These advantages are not offset by difficulties in catalyst manufacture, as is the case for previous designs.