The level of study of this class of compounds has sharply increased over the last 10-15 years, and investigations have produced important new data which we have considered systematically in previous reviews on the chemistry of the azaindoles [1-3]. This period has seen the development of new approaches in synthesis, for generating azaindole structures; among these methods, lithium-organic methods [4-6] and intramolecular Diels-Alder reactions  seem to have the greatest potential. Many studies have reported the mutual effects of oppositely directed shifts in aelectron density in N-heteroatomic rings; this is of general theoretical interest in organic chemistry. The results of these studies, especially over the last decade, lead to a variety of practical consequences. Investigation of the ligand properties of the azaindoles represents a new direction in studies of their chemistry these properties are involved in the formation of complexes, whose physical, chemical, and biological properties have also attracted interest [8-10]. Further studies have focused on the synthesis of glycosylated derivatives of azaindoles, which are isoelectric with purine, and are analogs of substances with known profiles of biological activity. For example, analogs of purine and pyrimidine deoxyribofuranosides have been prepared, and have been found to have powerful inhibitory effects in relation to human immunodeficiency virus ". 1-N-Glycosylated azaindoles, which are regarded as a model for dideazaadenosine glycosides, are interesting as antiviral and antitumor agents [12-15]. C-glycosylated aza analogs of indole have also been prepared . Azaindole molecules have been used for modeling of compounds of the ellipticin series [17-19], this being a new antitumor preparation. The spectrum of the biological effects of the different azaindoles has been significantly widened; patented agents have recently been described which are useful in the treatment of a wide variety of diseases. New data have been obtained from biological investigations on the uptake of 7-azaindole analogs of tryptophan and heteroauxin into cellular metabolism [20-26]; azaindoles have been used to prepare analogs of porphobilinogen [27, 28]. A single article cannot encompass all the areas involving azaindoles; we will thus restrict ourselves to data on fully or partially hydrogenated azaindole systems, except for systems in which aromaticity is disrupted by tautomerization, and azaindolines. Studies published up to 1978 are mentioned only as exclusions to the general rule, when they are needed for understanding a problem as a whole.