Background: Intravenous alteplase is licensed for treatment of ischaemic stroke within 3h of onset. Up to one-third of patients in the UK present to hospital within this time window but few are treated. Aims: To examine the effect of a stroke thrombolysis protocol on service provision for an acute stroke service in the UK, jointly run by Neurology and Medicine for the Elderly providing a comprehensive stroke service to a local population of 370 000. Design: Prospective observational study. Methods: Data collected prospectively for all thrombolysis referrals over a 12-month period beginning July 2004. Results: One hundred and eighty-eight patients were referred for potential thrombolysis, 129 transferred, 102 had an ischaemic stroke and 49 received intravenous thrombolysis. Referral rates from primary care and accident and emergency increased after guideline dissemination. Forty-three percent of the 49 patients treated with intravenous rt-PA achieved independence (modified Rankin Scale score 0-2) at 3months. Conclusions: A high proportion of ischaemic stroke patients can be treated with alteplase within 3h of onset with organized hospital services and dissemination of a simple referral protocol to local primary and secondary care services.