Elevated systolic blood pressure levels (> or =160 mmHg) are a common complication of acute stroke, affecting up to 60% of patients, and providing an immediate management dilemma in the 40% of acute stroke patients on pre-existing antihypertensive therapy. There are theoretical reasons for both lowering blood pressure in the acute stroke situation, as well as leaving raised levels untreated. Furthermore, low systolic blood pressure levels (< or =140 mmHg), though a less common problem affecting approximately 20% of patients, may also be associated with increased morbidity and mortality. However, limited data exists from randomised, placebo-controlled trials to inform as to the optimum management of acute stroke blood pressure. This review will consider the evidence for and against the therapeutic manipulation of acute stroke blood pressure, and discuss the information currently available from observational and therapeutic intervention trials, as well as consider the ongoing clinical trials in this area.