After a brief introductory chapter, the main part of this textbook deals with the preparation and chemical properties of the principal types of organosulfur compounds. In choosing examples to illustrate the text, the guiding principle has been that the illustrations should provide insight into and an understanding of the characteristic features of organosulfur chemistry. Two concluding chapters deal, on the one hand, with applications of organosulfur compounds in organic synthesis and, on the other, with a brief summary of organoselenium chemistry, highlighting the similarities and differences with respect to organosulfur chemistry.