Detection of paroxysmal atrial fibrillation (PAF) in patients with recent ischemic stroke or TIA suggests a cardioembolic etiology and leads to initiation of oral anticoagulation in suitable candidates. We assessed the diagnostic and therapeutic impact of adding ambulatory electrocardiography (24 hr ECG) to a standardised ischemic stroke workup. METHODS: We measured the frequency of detection of PAF in consecutive stroke patients who underwent 24 hr ECG that was not diagnosed clinically or on a standard 12-lead ECG. RESULTS: One hundred forty five ischemic stroke patients were included. 24 hr ECG was obtained in 136 patients (93.8%). Clinically unsuspected PAF was detected on 24 hr ECG in 7 patients (5.1%). The secondary prevention measure changed from antiplatelet agents to oral anticoagulation in 6 of 7 patients. CONCLUSION: Our findings suggest that ambulatory electrocardiography is a valuable diagnostic tool in the workup of stroke patients. Further prospective studies are needed to identify, subtypes of patients in whom the yield of ambulatory electrocardiography is higher.