This research is based on semi-structured interviews with thirty-two people who understand themselves to be suffering from health problems called ecological illness, or environmental hypersensitivity. The research examines the experience of ecological illness. Given that the medical status of ecological illness is controversial, and that troubles considered to be ecological illness are typically vague and non-specific, the study focuses on meanings and interpretive frameworks that are applied in the definition of such troubles; by those affected, by significant others, and by physicians. The analysis examines the nature and course over time of definitions of trouble-related identity and the social psychological and practical consequences of such definitions for respondents' illness experience. Because respondents largely define their troubles as physical health problems, a central issue in the analysis is the medical and social legitimation of illness claims. The research found that, in the course of seeking medical treatment and legitimation for their problems, people's experiences of trouble were typically discredited. They were long unable to resolve conflicts between a self-identity as sick and others' assessments of them as "not sick" or psychologically troubled. While the eventual diagnosis of hypersensitivity was a profound relief to people in many respects, it was often not recognized and accepted by others as a basis for informal or "official'' sick role considerations. Because of scepticism toward the concept of multiple sensitivities, many people continued to feel stigmatized by their problems. The study illustrates the impact and significance of controversies within medicine for the experience of certain kinds of health problems. / Thesis / Master of Arts (MA)