Studies reported here explicate “quantity of coverage theory” (QCT), which explains how The New York Times and other US mass media are influential but not all powerful in setting the world's environmental risk agenda. Beginning in 1987, the Times and its news sources brought an array of global environmental problems – ozone depletion, greenhouse warming, rain forest destruction, and biodiversity – to American attention, and these concerns quickly spread to other nations. However, by 1991 journalists were turning to other news, and the “endangered earth” lost their importance as a public problem. News media of each nation pay most attention to their own problems. Beyond that natural consideration, it appears from a variety of data that foreign journalists attend more to risks regarded important in the US, than American journalists attend to risks regarded important elsewhere. This is well illustrated by the deep concern of Europeans and the European press about genetically modified food, an issue to which the US press and public remain largely indifferent. Sixteen nations, all participants in the International Social Survey Programme, measured risk perceptions in surveys given in 1993 and repeated in 2000. Between these years, changes in risk perception varied considerably from one nation to another. Filipinos, especially, but also the Spanish, Israelis, Russians, and Japanese considerably increased their ratings of danger for nearly all hazards. Conversely, Germans, Bulgarians, and the Irish saw the same hazards as less dangerous in 2000 than they did in 1993. Were changing risk perceptions the result of changes in media coverage within each nation? For ten of the 16 nations, trends in news coverage of “environment” could be obtained from computer databases. Except Ireland, the nations with rising news coverage were those with increasing perceptions of environmental danger, while nations with falling news coverage showed decreasing perceptions of environmental danger. These results support QCT. The implication of QCT for risk managers is inescapably simple: public concern about an alleged hazard waxes with increasing news coverage and wanes with diminishing coverage. The specific content of the news is not particularly relevant as long as it suggests the possibility of danger or simply of uncertainty.