Hypertension is associated with a poor outcome in acute stroke. Paradoxically, lowering blood pressure (BP) may also worsen outcome, probably by reducing regional cerebral blood flow and worsening ischaemia. However, no large randomised controlled trials (RCTs) have directly studied the effect of BP reduction or elevation on outcome following stroke. Instead, advice on the management of BP in acute stroke is derived from small trials, case reports and anecdotal experience, and indirectly from RCTs where BP reduction was associated with a poor outcome. A systematic review of existing RCTs in acute stroke where drugs were administered which have the potential for altering BP will answer questions about the relationship between BP changes and outcome. A suitable large RCT of BP lowering or elevation could then be designed based on the findings of the review. Drugs that have been assessed in acute stroke and may lower BP include angiotensin-converting-enzyme inhibitors, beta-blockers, calcium antagonists, magnesium, naftidrofuryl, pentoxifylline, piracetam, prostacyclin and vinpocetine; those that may elevate BP include dobutamine, dopamine and hypervolaemic haemodilution. We have initiated a systematic review, under the auspices of the international Cochrane Collaboration and its Stroke Review Group, which aims to assess the relationship between drug-induced BP changes and outcome. We invite trialists or relevant studies (and systematic reviewers of such drugs) to join this collaborative project by contacting us.