Over the past several years, considerable public and private efforts in this country have been directed at reducing the risk of cancer that human exposure to high levels of radon gas poses. These efforts appear to have succeeded in raising public awareness of radon and in increasing testing for radon. For the most part, however, these efforts have been directed toward homeowners and have not addressed the problem of radon in residential rental properties. Yet, in 1989, nearly 34 million homes—over one-third of all housing units in the country—were rental units. The vast majority of these units are either single-family homes or are located at or below the second floor of a building, where experts believe radon is concentrated. This Dialogue explores the problem of high radon levels in rental housing and discusses some of the legal and policy tools available for reducing radon risks.