['Atrial fibrillation (AF) is a common cause of ischemic stroke and transient ischemic attack (TIA). More extensive diagnostic effort is required to detect paroxysmal AF (pxAF) than persistent AF (pAF); the prevalence of pxAF in stroke patients is unknown. We evaluated the prevalence of pAF and pxAF in ischemic stroke and TIA patients.', 'Consecutive patients with acute ischemic stroke/TIA were enrolled prospectively. We aimed to detect patients with a history of AF, with AF newly diagnosed in the emergency room (ER), or with newly diagnosed AF during a 3-month period following the event. Differences in the frequency of AF diagnosis with respect to the disposition of patients after ER work-up were assessed.', 'A total of 692 patients were enrolled (male: 52.2%; ischemic stroke: 69.1%; TIA: 30.9%). A previously documented history of AF was present in 19.7% (pAF: 47.1%, pxAF: 52.9%). In 3.8% of patients, AF was newly diagnosed in the ER (pxAF: 61.5%) and in 5.2% during the 3-month follow-up period. The overall prevalence of AF was 28.6% (pxAF: 62.6%). Previously documented pxAF evaded diagnosis at ER presentation in 48.6%. The prevalence of AF increased with age (p < 0.001). Patients with pxAF were younger than those with pAF (p = 0.004) and more often female (p = 0.05). The presence of any AF was associated with higher initial NIHSS scores (p < 0.001) and higher modified Rankin scores after 3 months (p < 0.001).'] Is paroxysmal atrial fibrillation more prevalent than persistent atrial fibrillation in acute stroke and transient ischemic attack patients?