This is the seventeenth annual volume of Progress in Heterocyclic Chemistry, which covers the literature published during 2004 on most of the important heterocyclic ring systems. The volume opens with two specialized reviews: Dennis Wright covers Furans as Versatile Synthons for Target-Oriented and Diversity-Oriented Synthesis; and John Hepworth and Mark Heron discuss "The Synthesis and Photochromic Properties of Naphthopyrans" The remaining chapters examine the recent literature on the common heterocycles in order of increasing ring size and the heteroatoms present.