This volume of Progress in Heterocyclic Chemistry (PHC) is the eleventh annual review of the literature, covering the work published on most of the important heterocyclic ring systems during 1998, with inclusions of earlier materials as appropriate. In addition, this year there are three specialized reviews. Martine Demeunynck and Arnaud Tatibouët present recent chemistry of Tröger's Base in Chapter 1. Pedro Merino reviews the reactions of metalated heterocycles with carbonyl compounds in Chapter 2. John Joule summarizes the remarkable nucleophilic substitution chemistry on the indole five-membered ring in Chapter 3. The subsequent chapters deal with recent advances in the field of heterocyclic chemistry arranged by increasing ring size and with emphasis on synthesis and reactions. Due to the ever increasing amount of material to be surveyed, the authors were encouraged to provide selective and critical reviews of the more significant papers where space does not allow comprehensive coverage.