The possibility to influence the performance of a heterogeneous catalyst by tailoring the size and shape of catalyst particles, their porous texture and the distribution of active sites within them should be exploited when developing a catalyst for a given process. This should be done within the context of the total process requirements, giving consideration to kinetic and mass transport as well as hydrodynamic requirements of the selected reactor configuration. The present paper discusses catalyst particle design in the above context and provides some guidelines on the choice of the important factors for heterogeneous catalyst particles. Rather than viewing a heterogeneous catalyst as some form of "catalytic substance", a heterogeneous catalyst should be considered as a part of a catalytic system of which the design involves catalytic site engineering, catalyst particle engineering and reactor engineering.