The March 1979 accident at Three Mile Island provided physicians specializing in radiation medicine an opportunity to observe the field under conditions never seen before. Since no, injuries occurred at the site or within the community, medical personnel were immediately involved in efforts to allay fear, provide accurate information, and replace labortory resources rendered ineffective by the release in the reactor building. Valuable insights concerning medical emergency planning are derived from the accident; suggestions are made for handling any future mishaps.