The effect of an intravenous infusion of recombinant tissue plasminogen activator on hemorrhagic transformation early after middle cerebral artery territory ischemia was studied in an established awake nonhuman primate (baboon) model. Following 3 hours' occlusion of the middle cerebral artery and 30 minutes' reperfusion in each of 30 baboons, a 60-minute infusion of recombinant tissue plasminogen activator (at three doses: Group A, 0.3 mg/kg, n = 6; Group B, 1.5 mg/kg, n = 6; Group C, 10 mg/kg, n = 6) or normal saline (n = 12) was undertaken. The frequency and volume of intracerebral hemorrhage, the volume of infarction, and clinical alterations were determined by computed tomography at 24 hours and 10 days, neuropathology at 14 days, and serial daily neurologic evaluations, respectively. Peripheral (nonintracranial) hemorrhage (Group A, p = 0.46; Group B, p = 0.015; Group C, p = 0.002) and peak plasma tissue plasminogen activator levels varied directly with the dose of recombinant tissue plasminogen activator. Petechial hemorrhagic infarction was a common finding among the 30 baboons. No significant differences in the incidences or volumes of infarction-related hemorrhage were apparent in any group compared with the respective saline-treated baboons. In pooled data, no significant relation between the volume of hemorrhage and the volume of infarction could be established. We conclude that the incidence and severity of hemorrhagic transformation are not related to infarction size and that recombinant tissue plasminogen activator does not increase the incidence or severity (volume) of hemorrhage when given early (less than or equal to 3.5 hours) after the onset of focal cerebral ischemia in this model.