Focusing on ABC, NBC, and CBS's evening news broadcasts from January 1984 through February 1986, a study examined network news coverage of environmental risk--defined as manmade chemical, biological, and physical agents that create risk in the indoor, outdoor, and occupational environments. Using the Vanderbilt University "Television News Index and Abstracts" as a database, 564 environmental news stories were studied for the extent of environmental risk coverage, the kinds of sources used, and the similarities and differences in coverage of major acute and chronic environmental risk stories. Environmental risk reporting was also compared to coverage of other risks. For this study, 12 environmental risk categories were created, consisting of three issue-oriented categories (Bhopal gas leak, acid rain, Agent Orange), five topical categories (including hazardous waste and oil/gas releases), and four broader categories (including air and water pollution). Coverage was assessed in terms of the number of stories, the length of stories, the number of field reporters used in the coverage, and the number of film reports produced. Results revealed that networks appeared to be using the traditional journalistic determinants of news (timeliness, proximity, prominence, consequence, and human interest) plus the broadcast criterion of visual impact to determine the degree of risk-issue coverage. Little relationship was found between amount of coverage and public health risk. (Three tables of data are included, and lists of the 12 types of environmental risk stories and sources, and 28 references are appended.) (MM)