The main objective of this book is to present the recent applications of photodynamic therapy (PDT) in treating cancer and other diseases. The limitations associated with current PDT agents, and the synthetic designs that have been used in various laboratories are also discussed. The utility of certain tumor-avid agent for cancer imaging (fluorescence, PET, MRI) is also summarized. The book also includes the use of delivery vehicles, including nanoparticles in improving the tumor-specificity of the desired agents. The book is basically focused on the translational approach of drug development. By providing certain specific examples, a clear concept of moving a "product" from the bench to bed-side is also discussed. To have a clear concept of drug development the book is divided in three parts — Medicinal Chemistry, Mechanistic and Clinical studies. Each part includes the contributions from the leading scientists with extensive experience in the respective field. The handbook is assembled by renowned scientists Dr Dougherty, known as the father of PDT, Dr Kessel, well known for his contributions on mechanism of PDT and Dr Pandey for his inventions in developing improved agents for PDT and cancer-imaging.