Objective. —To test the hypothesis that symposia on environmental tobacco smoke (ETS) are more likely to present unbalanced data and be authored by tobacco industry—affiliated individuals than journal articles on ETS. To compare the publication records and affiliations of authors of symposia with the authors of scientific consensus documents on ETS. Design. —Content analysis of articles; computerized literature searches of English-language publications (except for one symposium) supplemented with additional sources. Participants (Articles). —All 297 symposium articles on ETS and a random sample of 100 journal articles on ETS published between January 1, 1965, and March 31,1993; the 1986 Surgeon General's report on ETS; and the 1986 National Research Council's report on ETS. Main Outcome Measures. —For each article, regardless of whether it had a methods section, agreement with the tobacco industry position that ETS is not harmful; topic; funding source(s); affiliation(s) of author; and publication records of authors. Results. —Of the symposium articles 41% were reviews, compared with 10% of journal articles. A total of 83% of original symposium articles and 100% of journal articles contained methods sections (P=.0001). Symposium articles were more likely to agree with the tobacco industry position (46% vs 20%), less likely to assess the health effects of ETS (22% vs 49%), less likely to disclose their source of funding (22% vs 60%), and more likely to be written by tobacco industry—affiliated authors (35% vs 6%) than journal articles (P=.0001). Symposium authors published a lower proportion of peer-reviewed articles (71% vs 81%) (P=.0001) and were more likely to be affiliated with the tobacco industry (50% vs 0%) than consensus document authors (P=.0004). Conclusions. —Symposium articles on ETS differ from journal articles and consensus documents in ways that suggest that symposia are not balanced. (JAMA. 1994;271:612-617)