OBJECTIVES: Early Neurological Deterioration (END) occur in up to 25% of patients with ischaemic stroke receiving stroke-unit-care and in 11-13.8% of patients treated with iv-tissue-Plasmniogen-Activator (iv-tPA). The aim of the study was to establish and compare the prevalence of END and symptomatic Intracranial Hemorrhage (sICH) in a prospectively designed registry of consecutive patients treated with iv-tPA to a historic cohort of iv-tPA eligible patients whom were hospitalized prior to implementation of iv-tPA-treatment but receiving otherwise comparable acute stroke care. PATIENTS AND METHODS: Single center registry from a public Danish stroke-unit. Three-hundred-sixty-one unselected consecutive iv-tPA-treated patients admitted within 4.5 h from symptom-onset with symptoms of acute stroke and >17 years of age. The iv-tPA-treated cohort was compared to a pre-tPA cohort of 246 iv-tPA-eligible patients who were admitted to the same stroke center from 1998 to 2001. Acute stroke care apart from iv-tPA was comparable. Outcome measures was assessed on admission and at 24 h; END as any increase in National Institute of Health Stroke Scale (NIHSS) and symptomatic Intracranial Hemorrhage (sICH) with use of CT-head-scan. RESULTS: END was observed in 27 (7.5%) of the 361 patients in the tPA-cohort and 43 (17.5%) of 246 in the pre-tPA-cohort, p < 0.0001. Any ICH was detected in 23 (6.4%) and sICH in 3 (0.8%) of the iv-tPA-treated patients. CONCLUSION: END is significantly less frequent in acute stroke patients treated with iv-tPA. Deterioration due to ICH was rare and of limited severity in this population. END though remains a significant complication after stroke why more detailed knowledge on the various causes of END is needed to further improve patient outcome.