Oqab Z, et al. - This systematic review aims to establish the prevalence of pulmonary embolism (PE) in patients presenting with syncope to the emergency department (ED) and in hospitalized patients. In patients presenting with syncope, the estimated prevalence of PE is low. The Prandoni et al. estimates are significantly higher, implying a possible site effect, accrual bias, or investigation strategy. These and the prognostic effect of higher PE prevalence require understanding before changes in practice.