The role of systemic hypertension in acute coronary syndrome (ACS) has not been well studied. We studied consecutive subjects admitted to the University of Michigan Health System (Ann Arbor, Michigan) with symptoms of ACS. Data were collected using a standardized form. This observational study is currently ongoing; we collected data from May 1999 to December 2000 for 979 subjects, 890 of whom also had 6-month follow-up data. Hypertensives represented 64.4% (n = 630) of the total population. In general, hypertensive patients were older than normotensives (66.3 vs 59.9 years, p <0.0001), more often women (38.7% vs 26.9%, p = 0.0002), and had more comorbidities, such as previous myocardial infarction (47.9% vs 33.8%, p <0.0001), congestive heart failure (25.7% vs 12.0%, p <0.0001), and diabetes (36.9% vs 17.8%, p <0.0001). At admission, hypertensives had higher systolic blood pressure. Hypertensives had fewer electrocardiographic abnormalities indicating ischemic changes (67.9% vs 76.3%, p = 0.01) and had fewer incident of acute myocardial infarction (AMI) (70.7% vs 76.1%, p = 0.07) than normotensives. There was consistency over different levels of admission systolic blood pressure. Hypertensives received more oral cardiovascular drugs, and had undergone more invasive procedures. The lower rate of AMI in hypertensives seemed to be related to the higher frequency of a history of percutaneous coronary intervention and coronary artery bypass grafting. However, at 6-month follow-up, age- and gender-adjusted odds ratios for adverse events were equivalent in hypertensives and normotensives, suggesting no continuing differential treatment benefit for hypertensives in the months after the initial ACS episode.