OBJECTIVES: Clinic studies demonstrate that people diagnosed with environmental illness experience high levels of disability and health care utilization. Even though the controversial status of this disorder attracts attention, actual prevalence estimates and estimated impact on health care systems are unclear. To address this, we sought both a prevalence estimate and a measure of the degree of health care utilization for those reporting this diagnosis. DESIGN AND METHODS: Point prevalence, as assessed by self-report of professional diagnosis, was established with data from the Nova Scotia Health Survey 1995, a stratified, random sample population survey of 3227 Nova Scotian adults. We compared medical care utilization for the year following the survey, drawn from the provincial medical insurance register, between the 24 cases with no other reported medical conditions and 48 age-, sex-, and education level-matched healthy controls. RESULTS: The adjusted point prevalence of environmental illness was 2.6%. Physician reimbursement costs across the following year were 5.5 times more likely to be above the survey average ($259 CAD) when compared to the healthy control group. CONCLUSIONS: The prevalence of environmental illness diagnoses represents a significant disability and treatment burden, justifying research into case definition and the phenomenology of environmental illness by health psychologists.