We studied the prognostic influence and evolution of blood pressure during the acute phase of stroke in 89 patients (50 men and 39 women) with an average age of 69.4 +/- 10.8 years. Seventy-two were diagnosed as having ischaemic infarct and 17 as having spontaneous intracerebral haemorrhage. Blood pressure was taken every four hours for twelve days. Clinical situation was evaluated using the Rankin scale. Systolic and diastolic blood pressure progressively decreased without needing any medication in the first two weeks of evolution. The decrease was greatest in hypertense patients and in those with left ventricle hypertrophy. We found the initial figures for systolic and diastolic blood pressure significantly higher in those patients with brain infarct who had not died and in those in a better functional position the second week of evolution. Blood pressure did not influence the prognosis of intracerebral haemorrhage patients.