Dr. Ottto Warburg won a Nobel prize showing the primary cause of cancer was oxygen deprivation at the cellular level and a second prize nomination for his discovery that cancer cannot live in the presence of oxygen. Medical ozone therapy has been used for three quarters of a century to effectively treat cancer. Dozens of published papers and studies show its benefits against this life taking disease. We will discuss the history of its use, the biochemistry of how its works and its effectiveness against cancer.