This article analyzes 1,609 responses to a Massachusetts survey on physicians' knowledge and practice in the detection and treatment of environmentally induced illness. One would assume that practicing in a Superfund site area would heighten awareness among physicians. Yet physicians who practice in communities with Superfund sites are no more knowledgeable about environmental health hazards than those who practice in communities without Superfund sites. Physicians specializing in occupational/preventive medicine are the most knowledgeable about environmental health hazards, whereas obstetrician/gynecologists are the least knowledgeable. Self-rated knowledge of environmental health hazards was found to be strongly related to knowledge about the Right-to-Know law and also to the likelihood of asking questions about workplace and nonworkplace environmental exposures. Physicians who perceive that nonworkplace environmental hazards are very important are more knowledgeable about medical interviewing, diagnostic criteria, and the Right-to-Know law than those who rate environmental health hazard information as "irrelevant to my practice." This article examines the role of physicians in the detection and treatment of environmentally induced illness. It is important to investigate these issues because of increasing scientific knowledge of toxic health