In this volume, Drs. Parrick and Shaw have upgraded their earlier chapter on pyridazines, cinnolines and Dr Hurst and Dr McCullough have done the same for their chapters on the subjects of pyrimidines and quinazolines and pyrazines, respectively. Dr Bolton has contributed to this series several times before, but not on the subject of phenazine, oxazine and thiazine sulfur dyes. However, his wide experience in heterocyclic chemistry enabled him to analyse recent progress in this area without difficulty and with his customary skill. Professor Johne returns to one of his research interests, quinazoline alkaloids, while Professor O'Shea completes the volume with a timely review of six-membered rings with three or more heteroatoms: triazines, tetrazines, pentazines and hexazines.