It is hoped that the organization of this monograph will prove to be selfexplanatory, but a few general observations are in order.Chemical compounds are tabulated exhaustively by the principle of latest position. Thus halogenated pyridinecarboxylic acids are found in Chapter X rather than VI, but hydroxy acids in Chapter XII. The principal exceptions are the quaternary compounds, which proved too numerous to be catalogued, and the N-oxides, which are included in Chapter IV irrespective of nuclear substitution. Other exceptions are explained where they occur.The principle of latest position does not apply to reactions. All reactions for obtaining pyridine derivatives from non-pyridinoid starting materials are covered in Chapter I1 irrespective of substitution. If the starting material is a pyridine derivative, the reaction is discussed instead in the appropriate later chapter or chapters. Thus the conversion of aminopyridines to pyridinols is discussed in Chapters IX and XII.Nomenclature follows Chemical Abstracts.The editor wishes to express his gratitude to Prof. D. S . Tarbell of the University of Rochester for the impetus he gave to this undertaking, to the chemists in many parts of the world who have been so generous with reprints, to the staff of Interscience Publishers for their cooperation, and finally to Dr. R. S. Long and Dr. J. J. Leavitt of American Cyanamid for their patience. ERWINKLINCSBERG vii Contents of Other Parts Part One I. Properties and Reactions of Pyridine and Its Hydrogenated Derivatives. By 11. Synthetic and Natural Sources of the Pyridine Ring.