The monograph analyzes the structure and reactivity of porphyrins from the standpoint of the concept of macrocyclic effect, proposes new types of classification of these compounds based on differences in the spatial structure and nature of the polarization of molecules. The book in a condensed form contains an analysis of data on spectroscopy, thermo-, photo- and electrochemistry, elements of quantum chemistry, as well as on the kinetics and thermodynamics of reactions of coordination and acid-base interaction and other issues of porphyrin chemistry. The bibliography includes about 1000 references to domestic and foreign literary sources.