Following the study protocol, we stratified the 615 patients of ECASS I according age (< or =/-70 years) and analysed the response to intravenous rt-PA in both subgroups. The older patients (248) suffered from the same stroke severity as the younger patients (367) experienced, however, a more severy clinical course (placebo group after 3 months after stroke: Barthel Index 50 vs. 85, mortality 24% vs. 11%). Treatment with rt-PA increased the proportion of undisabled patients at 3 months after stroke onset significantly only in the younger patients. The risk for brain parenchymal hemorrhage was increased by the factor of 4.7 and 4.6 in both age groups. It is obviously harder to achieve an undisabled state by systemic thrombolysis in the elderly. Facing the risk of brain hemorrhage associated with rt-PA, the risk-benefit-ratio may be less favourable in patients over 70 years.