The use of high-energy protons for radiation therapy was first proposed by Wilson in 1946. Then, at five major centers, Berkeley (United States). Dubna (Russia), Uppsala (Sweden), Harward (United States) and Moscow (Russia), between 1950 and 1960 the use of proton therapy followed. In the beginning progress was slow: 1) Because proton dosimetry and imaging techniques for tumor localization were not well developed 2) Because the accelerators used to produce the proton beams were designed as experimental facilities rather than as clinical machines. More recently, significant growth has occurred in the number of accelerators used for proton therapy. The number of centers has significantly increased over the past decade and protons are now used with more routine in multiple disease sites worldwide.