Recent studies suggest that their is a relatively high incidence of silent paroxysmal atrial fibrillation (PAF) in cryptogenic ischemic stroke patients. Detection of silent PAF in this population, however, requires prolonged cardiac monitoring. On the other hand, there is no understanding of the frequency of silent PAF in patients with a "known" or presumed etiology for their ischemic stroke other than AF. If this incidence is also found to be significant, a dramatic change in stroke evaluation and management would likely occur. This study intends to find the incidence of PAF in a population of recent (within 7 days) ischemic stroke patients (or MRI positive "transient ischemic attack (TIA)" patients) who have presumed etiology for their stroke other than atrial fibrillation or other high risk cardiac lesion. Stroke etiology will be determined through a standard post-stroke evaluation that includes: