We've all heard of Roentgen, but who is Mark Carrol? Roentgen's 1895 discovery of X-rays was publicized worldwide in January of 1896. By the end of that same month, cancer radiotherapy in the U. S. had begun. Some early treatments were quite impressive considering the limited base of knowledge at the time. Advances in physics over the past 50 years have recently been enhanced with mathematical and computational applications causing tremendous technological advances in radiotherapy techniques. Some of the concepts to be discussed are Monte Carlo calculations, intensity modulated radiation therapy and inverse computational treatment planning techniques. Actual clinical examples will be presented along with a look into the future.