To determine the risk factors and frequency of intracranial hemorrhage among patients undergoing thrombolysis for pulmonary embolism. A retrospective descriptive and controlled analysis. Hospitalized patients at centers in the United States, Canada, and Italy. All had evidence of pulmonary embolism on perfusion scans or angiography. None. Data were analyzed on 312 patients from five previously reported studies of pulmonary embolism thrombolysis. The frequency of intracranial hemorrhage up to 14 days after pulmonary embolism thrombolysis was 6 of 312 or 1.9% (95% confidence interval, 0.7 to 4.1%). Two of six intracranial hemorrhages were fatal. Two of the six patients received thrombolysis in violation of the protocol because they had pre-existing, known intracranial disease. Average diastolic BP at the time of hospital admission was significantly elevated in patients who developed an intracranial hemorrhage (90.3 +/- 15.1 mm Hg) compared with those who did not (77.6 +/- 10.9 mm Hg; p = 0.04). Other baseline characteristics and laboratory data were similar in both groups. Decreased level of consciousness, hemiparesis, and visual field deficits were the most common clinical signs of intracranial hemorrhage. Intracranial hemorrhage after pulmonary embolism thrombolysis is an infrequent but often grave complication. Meticulous patient screening before administering thrombolysis is imperative. Diastolic hypertension at the time of hospital admission is a risk factor for intracranial hemorrhage after pulmonary embolism thrombolysis.