Radiation oncologists, medical physicists, dosimetrists, radiation therapists, radiation oncology nurses and nurse practitioners, biologists, physician assistants and practice administrators comprise ASTRO's more than 10,500 members, making it the largest radiation oncology organization of its kind. These medical professionals, found at hospitals, cancer treatment centers and academic research facilities around the globe, make up the radiation therapy treatment teams that are critical in the fight against cancer. Together, these teams, treat more than 1 million cancer patients each year.

ASTRO provides members with the continuing medical education, health policy analysis, patient information resources and advocacy that they need to succeed in today's ever-changing health care delivery system.