As pharmaceutical companies race to find new and novel drugs faster, the tools of combinatorial chemistry are increasingly playing a larger role. Chemists can now prepare hundreds or thousands of analogs simultaneously to reveal structure-activity relationships (SAR) all at once and potentially shorten the discovery process for new drugs by years. A wide variety of solid-phase organic chemistry techniques have evolved for the preparation of chemical libraries, such as H.M. Geysen et al.'s (1984) pin method, R.A. Houghten's (1985) tea-bag method, very large-scale immobilized polymer synthesis (VLSIPS), mix-and-split synthesis and soluble polymers. Solution-based techniques are also under refinement and several extractive techniques have been reported. Also, the use polymer-bound reagents and sequestration agents, for removing impurities, are being developed. An overview of chemical library techniques is presented.