PIP: This monograph includes a state-of-the-art discussion of pulmonary embolism, including its pathogenesis, predisposing factors, clinical presentation, diagnosis, and medical and surgical treatment. This remains one of the most common yet most difficult problems in medical practice. The disease affects 650,000 patients each year in the US, with over 200,000 fatalities. 40-60% of patients who die because of pulmonary emboli arrive at autopsy without the correct diagnosis and treatment. The major source of pulmonary embolism is the deep venous system of the legs and pelvis. Its frequency is greatest in patients ages 50-65 years, with no significant difference between men and women. An association has been identified with oral contraceptives. Figures in the monograph schematize an appropriate diagnostic plan of approach to the patient with suspected pulmonary embolism as well as a combined approach to both diagnosis and treatment. Elements of the latter include a history taking and physical examination for suspicion of pulmonary embolism, arterial blood gas, chest x-ray, electrocardiogram, ventilation-perfusion lung scan, pulmonary angiography, Doppler ultrasound, and thrombolytic therapy followed by heparin. A total of 572 references are cited.