Our purpose was to relate the outcome after local intra-arterial fibrinolysis (LIF) to the natural course in middle cerebral artery (MCA) occlusion. We retrospectively studied 40 patients with a dense middle cerebral artery on early CT; 20 were treated with LIF within 6 h of onset of symptoms, 20 received "conventional" stroke therapy. The dense middle cerebral artery, which is regarded as a highly specific indicator of thromboembolic MCA occlusion, was chosen as inclusion criterion since patients with "conventional" stroke therapy were not exposed to cerebral angiography. Patients treated with LIF had a significantly better outcome using the Barthel index (P = 0.025): there was a 30% increase in the proportion of patients with minimal or no disability. Mortality, however, did not differ significantly (P = 0.7). Two fatal haemorrhages occurred in the LIF group, and one haemorrhagic transformation in the "conventional" group. Leptomeningeal collateralisation correlated significantly with outcome in the LIF group (P = 0.04). Although the relation between outcome and interval from onset of symptoms to LIF was not significant (P = 0.74), all patients treated within 3 h had an excellent outcome.