This book summarizes and critically reviews the biochemical, chemical and pharmacological literature from 1885 to 1987 concerning a unique class of compounds derived from heme: the N-substituted porphyrins. Originally synthesized in laboratories to study effects of structural modifications on the properties of biologically essential porphyrins, they were found in the past decade to be natural products. They are deleterious by-products of drug metabolism in the liver and reactions of hemoglobin in the blood. In this book data for characterizing N-substituted porphyrins are summarized. A thorough analysis of the major reactions of these compounds, several unique in porphyrin chemistry, and a critical review of synthetic methods make this book the sole source for laboratory methods in this area available today. The comprehensive discussion of biochemical and pharmacological processes involving N-substituted porphyrins provides the first unified view of a broad range of experimental results from laboratories in Britain, France, Japan, and the United States.