Stroke is a major cause of death and disability in Ontario. This study estimates the cost of stroke, which can be used to help policymakers appreciate the burden this disease places on society. A prevalence-based study measured disease-related costs in 1994/95 incurred by people with stroke. Direct costs included expenditures on hospital and other institutional care, services of physicians and other health professionals, drugs, research, home care, emergency health services, assistive devices and community support. Indirect costs were measured using the human-capital approach, which examines lost productivity due to premature death and disability. A sensitivity analysis was used to estimate the total cost of stroke in Ontario to be $857 million, with a low of $719 and a high of $964 million. Direct costs were 60% of total costs. Stroke accounted for 3.9% of acute care hospital costs, 5.0% of rehabilitation, chronic care and other institutional costs, and 6.0% of home care costs. It accounted for a relatively minor proportion of physician costs (1.0%) and drug expenditures (0.3%). Stroke has a major economic impact in Ontario. Most direct costs of stroke are borne by the institutional health and community support sectors. These findings may provide guidance to policy-makers when they set priorities for research and prevention activities. Because provincial databases were used that contained more detailed information than national databases, cost estimates in this study are more precise than national estimates. Because a strict definition of stroke was used in this study, cost estimates may be considered conservative.