Dose distributions produced by using proton and ion beams in radiation therapy conform closely to the target volume maximizing the sparing of adjacent normal tissues and sensitive structures. Worldwide, through 2001, over 30,000 patients have been treated with proton beams and over 3,500 with ion beams. In 2002, there are 21 operating proton therapy facilities, including several hospital‐based dedicated facilities. Seven of these facilities are limited to treating eye tumors only. Carbon ions are available at two facilities in Japan and one in Germany. All existing centers use either a cyclotron or a synchrotron and several facilities have one gantry or more to provide beams at any angle to the patient. For several treatment sites, there are good long‐term follow‐up results, increasing the interest worldwide in having proton or ion beams more readily available. As a result many new facilities are under construction or being planned and some existing facilities are being upgraded. © 2003 American Institute of Physics