The book deals with the chromosomal imbalance (aneuploidy) theory of cancer. The book explains how gene mutations are not powerful enough to cause cancer, describes how cancer is initiated and why progression takes years to decades, and accounts for the global or macroscopic characteristics that readily identify cancer. In addition, it clarifies why cancer cells often become drug resistant even to drugs they were never exposed, provides objective, quantitative measures for detecting cancer and monitoring its progression, and suggests non-toxic strategies of cancer therapy and prevention. In short, it posits that the autocatalyzed progression of aneuploidy is carcinogenesis. The clarity and unifying simplicity of the theory of chromosomal imbalance has the potential to fundamentally alter the course of cancer research, prevention, diagnosis and treatment.