Abstract—Both low and high blood pressures (BPs) during the acute phase of stroke are associated independently with a poor outcome. Several small clinical trials have involved the alteration of BP, and this study assessed the relationship between change in BP and functional outcome. Randomized, controlled trials of interventions that would be expected, on pharmacological grounds, to alter BP in patients within 1 week of the onset of acute ischemic or hemorrhagic stroke were sought using electronic searches. Data were collected on BP and clinical outcome. The relationship between the differences in on-treatment BP and odds ratios for outcomes was assessed using meta-regression. Thirty-seven trials involving 9008 patients were included. A U- or J-shaped relationship was found among on-treatment BP difference and early death, death at the end of 90-day follow-up, and combined death or dependency at the end of follow-up. Although outcomes were not significantly reduced at any level of change in BP, the lowest odds occurred at the following times: early death (odds ratio: 0.87; 95% CI: 0.54 to 1.23), 8.1 mm Hg; death at the end of follow-up (odds-ratio: 0.96; 95% CI: 0.31 to 1.65), 14.4 mm Hg; and combined death or dependency at the end of follow-up (odds ratio: 0.95; 95% CI: 0.11 to 1.72), 14.6 mm Hg. Although large falls or increases in BP are associated with a worse outcome, modest reductions may reduce death and combine death or dependency, although the CIs are wide and compatible with an overall benefit or hazard.