The present book is an overview of the molecular genetics of cancer. Its objective is to summarize our current state of knowledge on the nature of cancer, types of carcinogens, the genetic basis of cancer, the characteristics of cancer cells, oncogenes, oncoproteins and anti-oncogenes the mechanisms converting proto-oncogenes into oncogenes and the role of viruses in causing cancer. Throughout the book emphasis has been to explain the molecular mechanisms underlying these processes. The target readers for the book are post-graduate students in biological sciences and medicine, and members of the medical profession who may wish to keep abreast in the basic processes underlying cancer.