BACKGROUND : Blood pressure (BP) is an important determinant of functional outcome in acute ischemic stroke (AIS) patients treated with intravenous tissue plasminogen activator (IV-tPA). Current guidelines recommend a BP target of 185/110 mmHg before IV-tPA bolus and maintaining it at less than 180/105 mmHg for the first 24 hours. However, the effect of blood pressure on various outcome measures after systemic thrombolysis remains unclear. METHODS : Following a systematic search of Medline and EMBASE, all observational studies reporting effect of pretreatment BP on 90-day functional outcome as measured by the modified Rankin Scale (mRS) and/ or incidence of symptomatic intracranial hemorrhage (sICH) in AIS patients receiving thrombolytic therapy were included. RESULTS : Of 2181 studies screened, 26 studies, involving 38,937 subjects, met inclusion criteria. Higher prethrombolysis systolic BP was significantly-associated with poorer 90-day functional outcome (Mean difference 3.87 mmHg; 95% confidence interval [CI] 1.18-6.56) and increased incidence of sICH (Mean difference 5.31; 95% CI 2.22-8.40). When studies were stratified by different cut-offs for functional outcome (mRS 0-1 versus 0-2) and definitions of sICH used (Randomized controlled trials or SITS-MOST), there was no significant difference in mean difference between the subgroups. CONCLUSIONS : Our data showed that higher prethrombolysis SBP was associated with poorer outcomes in thrombolysed acute ischemic stroke patients. This may suggest that more aggressive lowering of BP below the current recommendations prior to thrombolysis could be beneficial. The effect of early BP trends after tPA infusion could not be evaluated due to limited available data. Ongoing randomized clinical trials, like ENCHANTED, may provide further insights into the current guidelines and optimal BP levels.