Objectives. This study compared functional status in Americans and Canadians with and without prior symptoms of heart disease to separate the effects of medical care from nonmedical factors. Background. Coronary angiography and revascularization are used more often in the United States than in Canada, yet rates of mortality and myocardial infarction are similar in the two countries. Recent data suggest that functional status after myocardial infarction is better among Americans than Canadians, but it is uncertain whether this difference is due to medical care or nonmedical factors. Methods. Quality of life was measured in patients enrolled in seven American and one Canadian site in the Bypass Angioplasty Revascularization Investigation. Prior symptoms of heart disease were defined as angina, myocardial infarction or congestive heart failure before the episode of illness leading to randomization. Functional status was measured with the Duke Activity Status Index and overall emotional and social health using Medical Outcome Study measures on the basis of patient status before the index episode of acute ischemic heart disease. Results. Quality of life was generally better in the 934 Americans than in the 278 Canadians, with overall health rated as excellent or very good in 30% of Americans versus 20% of Canadians (p = 0.0001), higher median Duke Activity Status Index scores (16 vs. 13.5, p = 0.03) but equivalent emotional health (76 vs. 76, p = 0.74) and social health scores (100 vs. 80, p = 0.07). Among the 350 patients without prior symptoms of heart disease, Americans and Canadians had similar overall health, Duke Activity Status Index and emotional and social health scores. However, of the 860 patients with previous symptoms of heart disease, Americans had higher overall health (p = 0.0001) and Duke Activity Status Index scores (p = 0.0008) but similar emotional and social health scores. The results were essentially unchanged after statistical adjustment for potential confounding factors. Conclusions. The functional status of patients without prior symptoms of heart disease is similar in Americans and Canadians. However, among patients with previous symptomatic heart disease, functional status is higher in Americans than in Canadians. This difference may be due to different patterns of medical management of heart disease in the two countries.