In this volume three of the chapters deal with specific ring systems: 1,2,3-triazoles (T. L. Gilchrist and G. E. Gymer), dibenzothiophenes (J. Ashby and С. С Cook), and the 7-azabicyclo[2.2.1]heptadienes, and their reduced, and benzo-fused, derivatives (L. J. Kricka and J. M. Vernon). Three further chapters cover particular aspects of heterocyclic compounds in general: cationic cycloaddition reactions (С. К. Bradsher), homolytic aromatic substitution (F. Minisci and 0. Porta), and base-catalyzed hydrogen exchange (of ring protons) (J. A. Elvidge, J. R. Jones, 0. O'Brien, E. A. Evans, and H. C. Sheppard).