 The solid dispersion has become an established solubilization technology for poorly water-soluble drugs. Since a solid dispersion is basically a drug polymer-2 component system, the drug polymer interaction is the determining factor in its design and performance. In this review, we summarize our current understanding of solid dispersions both in the solid state and in dissolution, emphasizing the fundamental aspects of this important technology. This article was offered by Yen Bin Huang and Weiguo Dai.