This completely new and innovative textbook provides a comprehensive account of pericyclic reactions and organic photochemistry for undergraduate and postgraduate courses. The approach is based on mechanism and reaction type, and the subject matter is developed and concentrated on better understanding rather than on merely grasping factual knowledge. Major modifications have been made in chapters 3, 4, 5, 7, 8 and 10. Stereochemistry aspect has been discussed in great detail. A new chapter on Objective Problems and Their Solutions has been added, which may be of immense use for the students and teachers. Updates in the text have been made wherever necessary. This will prove a boon to the students preparing for the NET (CSIR), GATE, SLET, IAS and other competitive examinations.