Accurate diagnosis of pulmonary embolism is essential to minimize morbidity and mortality caused by failure to treat when necessary or by inappropriate treatment. Because clinical symptoms and signs are nonspecific, it is impossible to prove the diagnosis solely on clinical grounds. The diagnosis requires high level of suspicion, estimation of the pretest clinical likelihood of embolism, and judicious use of objective investigations (scintigraphy, computed tomography, or angiography) to confirm or refute the suspicion. The choice of tests depends on the availability of these tests, the hemodynamic state of the patient, and the presence of other cardiopulmonary diseases. Despite the availability of most accurate tests, pulmonary embolism will continue to be missed if not first considered by the physician.