Indoor air quality (IAQ) has recently been a subject of increased concern, because (1) indoor pollutant levels and exposures frequently exceed those encountered outdoors, (2) many new products are being introduced into the indoor environment that provide increased levels of exposure and (3) energy conservation measures that reduce ventilation rates can elevate indoor pollutant concentrations. The indoor pollutant which has attracted the greatest public attention to date is radon. This paper provides information on potential sources of radon, typical indoor levels, the relationship of energy-efficient construction to these levels, the potential health effects from exposures to radon progeny and effective control strategies to mitigate indoor radon levels in residences. In addition, this paper addresses how government and other organizations have responded to concerns about indoor radon exposures.