The 1990 International Symposium on Radon and Radon Reduction Technology was held on February 19-23, 1990, in Atlanta, Georgia. Sponsored jointly by the U. S. Environmental Protection Agency's Air and Energy Engineering Research Laboratory (EPA-AEEERL) and Office of Radiation Programs (EPA-ORP), the symposium was devoted to the exchange of current research developments on radon and radon reduction technology in the indoor environment. Education in radon research and the dissemination of technical information were the primary objectives of the meeting. Forty-seven oral papers, 13 panel presentations, and 45 poster papers were presented, with the keynote address focusing on the 'big picture' regarding radon risks and its reduction. The papers addressed a variety of radon topics: government programs, policies, and public information; health studies; radon measurement methods; radon surveys; entry dynamics; radon in the natural environment; radon reduction methods; radon prevention in new construction; and radon in schools and large buildings.