This is the sixteenth annual volume of Progress in Heterocyclic Chemistry, and covers the literature published during 2003 on most of the important heterocyclic ring systems. This volume opens with two specialized reviews. The first covers "Lamellarins: Isolation, activity and synthesis" a significant group of biologically active marine alkaloids and the second discusses "Radical Additions to Pyridines, Quinolines and Isoquinolines" The remaining chapters examine the recent literature on the common heterocycles in order of increasing ring size and the heteroatoms present.