Solid dispersion systems of prednisolone-cyclodextrins (CD) and prednisolone-polyvinyl-pyrrolidone (PVP) were prepared by the spray-drying method. The dissolution rates of prednisolone were markedly increased in these solid dispersion systems in the pharmacopeial disintegration medium at pH 6.8. In particular, the solid dispersion systems of prednisolone-CD inhibited and/or retarded the crystallization of prednisolone. The interaction of prednisolone with CD and PVP in water was also investigated. The apparent stability constants of the β- and γ-CD systems were both larger than that of the PVP system.