RolandE.Dolle (AdolorCorporation, Exton, PA) published the seventh comprehensive survey in an ongoing annual review series about combinatorial chemistry. Libraries demonstrating biological activity are described as well as libraries belonging to certain structural classes. Polymer-supported reagents and scavengers, polymer-supported linkers, and polymersupported chiral ligands are also listedwithmore than 400 references. Publications of large libraries (greater than 1000 members), which were prevalent in the late 1990s for broad screening purposes and structureactivity relationship (SAR) development, have given way to small, focused, compound arrays for lead optimization. Of the 120 biologically active libraries with a defined number of members, 79 percent have fewer than 500 members, 6 percent contained 500 to 1000 members, and 15 percent contained more than 1000 members. Researchers are increasingly utilizing both solidand solution-phase techniques to analogue multiple regions of a lead molecule to establish SAR (J. Comb. Chem. 2004, 6, 623).