Photoinduced charge-transfer reactions between adsorbed pyrene and N,N'-dimethylaniline (DMA) in zeolites are examined by fluorescence quenching and transient absorption spectroscopy. The quenching of pyrene fluorescence by DMA is found to be limited by the diffusion of DMA that is confined in zeolite supercages. The diffusivity of DMA is measured to be 8.4 x 10(-6) cm(2)/s in K+ ion-exchanged zeolite X. The resultant exciplex between pyrene and DMA is very short lived, and its decay leads to a large yield of ion radicals. Although no emission from the exciplex is observed in ionic zeolites within the experimental capability (i.e., fluorescence quantum yield Phi(f) < 0.001), it exhibits a normal fluorescence spectrum in a nonionic zeolite (Ultra Stable Y: USY) with a maximum around 460 nm, indicating a very weak interaction between the adsorbate and the host in contrast to its behavior in ionic zeolites. The large yield and the long lifetime of ion radicals are attributed to the high electric field and the strong ionic interaction within the supercage, which favors charge separation and dissociation of the exciplex into a cage-confined ion pair. The slow charge recombination reaction may be understood in terms of a charge stabilization effect characterized by a lower driving force for back electron transfer (-DeltaG(-et)) and a high media reorganization energy lambda(s). A charge stabilization effect is also observed in charge-shifting reactions where cations such as biphenyl and pyrene cation radicals are produced in zeolites by high-energy radiation. Quenching of the above cations by mobile DMA, conventionally observed as a diffusion-controlled process, is dramatically slowed. It is found that a significant amount of reorganization energy is required to promote charge-transfer reactions in ionic zeolites. Such unique properties of zeolites in charge separation and stabilization are distinct from those in other systems such as liquids and porous silica.