Blood pressure (BP) in healthy individuals exhibits a diurnal variation, with a nighttime dip of 10%-20%. A persistently high nighttime BP is associated with increased cardiovascular morbidity. The effects of diurnal BP variations on the neurologic deficit in acute stroke at presentation and in the first few weeks poststroke are unclear. We hypothesized that persistently elevated BP results in poor outcome. Patients with an acute ischemic stroke presenting within 48 hours of onset underwent 24-hour ambulatory monitoring of systolic, diastolic, and mean BP. There were a total of 35 patients (16 males; mean age, 74 +/- 14 years). The percentage change between mean day and night BP classified patients into dippers (>10% change), nondippers (0-10% change), or reverse-dippers (