Research and development on the preparation of novel polymer microspheres and their applications have been accelerated in this decade. This article deals with polymer catalysts and reagents which have functional groups on and in polymer microspheres or beads. Immobilization of functional groups on polymer microspheres causes not only simplification of the recovery of reagent from the reaction system, but also changes in the rate, selectivity, and pattern of reaction in most cases. Dependence of these changes on the physical and chemical structure of polymer microspheres is discussed and a guide is given for the preparation of polymer microspheres having desirable functions.