The majority of intracerebral haemorrhage patients present with markedly elevated blood pressure immediately after symptom onset. Management of blood pressure in the first 24 h is extremely controversial and lends itself to two competing rationales. There is some evidence that early treatment may improve outcome, potentially by reducing the rate of haematoma expansion. It is also possible that this will reduce cerebral blood flow and therefore exacerbate the cerebral injury, particularly in the region surrounding the haematoma. Only a trial that includes both randomisation of patients to two different blood pressure management strategies and actual measurement of cerebral blood flow can effectively address this pressing debate. This is the only unequivocal way to demonstrate the haemodynamic effects of rapid blood pressure reduction. The Intracerebral Haemorrhage Acutely Decreasing Arterial Pressure Trial is designed to test the hypothesis that blood pressure reduction does not result in significant or harmful changes in cerebral blood flow in acute intracerebral haemorrhage. Two hours after randomisation to a systolic blood pressure target of <150 or <180 mmHg, cerebral blood flow is measured using computed tomography perfusion, which is the primary end-point of the trial. A study of this type is critical to establishing the safety of early blood pressure treatment and is necessary for planning larger efficacy trials in a rational manner. This trial is registered with clinicaltrials.gov (NCT00963976).