Severely elevated blood pressure (BP) and aggressive BP reduction are both associated with poor outcome in acute ischemic stroke (AIS). In nontissue-type plasminogen activator patients, the American Heart Association recommends antihypertensive therapy only if BP is ≥ 220/120 mm Hg with a goal of 15% to 25% reduction in the first 24 hours. We hypothesized that patients with AIS often receive antihypertensives in the emergency department below the recommended threshold and that BP reduction is often >20%. In 2005, AIS cases were ascertained at all 16 hospitals in Greater Cincinnati. BP was recorded at emergency department presentation and before and after antihypertensive treatment. Hypertension was defined as BP ≥ 220/120 mm Hg. Chi-square and Mann-Whitney U tests were used for comparisons. A total of 1739 patients with AIS met inclusion criteria. Median age was 72 years with 43% male and 25% black. Of 218 treated with antihypertensives, 65 (30.0%) met treatment criteria immediately before treatment. Treated patients were younger (66 versus 73 years, P<0.001) with greater stroke severity than untreated patients (National Institutes of Health Stroke Scale score 4 versus 3, P=0.028). Median change in systolic BP was -25 mm Hg (range, -96 to 25 mm Hg). Median percentage change in systolic BP was -12.3% (range, -49.2% to 16.1%). Systolic BP decreased > 20% in 52 treated patients (23.7%). Only one third of patients with AIS treated with antihypertensives met American Heart Association-recommended treatment criteria, and the rate of change of BP was frequently greater than recommended. Further studies are warranted to determine the impact of practice patterns on AIS outcomes.