The aim of this study was to assess cerebral hemodynamics in patients with acute ischemic stroke undergoing thrombolytic therapy and to assess the relationship between cerebral hemodynamics and outcome. Forty-one unselected patients admitted to hospital within 3 h received intravenous thrombolytic therapy and were examined by extracranial and transcranial Doppler ultrasound examinations. Their strokes were clinically graded with the National Institute of Health Stroke Scale. Outcome after 3 months was graded with the modified Rankin Scale. Amongst the 27 patients who had an additional ultrasound examination 24 h after treatment, favorable outcome was significantly more common amongst patients with recanalization than amongst those without (P < 0.004). Thirteen patients with middle cerebral artery occlusions were continuously monitored during thrombolysis and frequently up to 5 h after start of thrombolysis. Early recanalization occurred in nine (69%), at a median delay of 178 min (range 140-287) after stroke onset. All of these nine patients had a favorable outcome. Recanalization within 24 h was associated with favorable outcome. Subgroup analysis suggests that this effect is mostly related to early recanalization within the first 5 h after stroke. Transcranial Doppler may therefore help to identify those patients most probably to benefit from thrombolysis, especially in those patients with a higher potential risk of complications.