The present concise text book has been revised extensively to cover this U.G.C. curriculum on Organic Photochemistry from its role and reactions to the photochemical mechanism in nine chapters. However, this book will also be useful for those students who are preparing for the competitive examinations such as NET (CSIR), SLET, IAS and PCS. Furthermore, this text book, of course, does not exclude its use by others such as research scholars, lecturers, professors, etc., who might gain some benefit from its contents. This text book includes introductory chapters on photochemistry and mechanisms of organic photochemical reactions. Extensive cross referencing has been avoided purposively to make the subject interesting.