Pulmonary embolism becomes an increasingly important problem as the extent of its incidence becomes unveiled. Although the subject of much study, the incidence of pulmonary embolism has remained a matter of uncertainty and disagreement. Pulmonary embolism is reported by some as being infrequent; it may, in fact, represent one of the most important forms of terminal illness, one of the commonest causes of death in the population at large. The diagnosis of pulmonary embolism is difficult and equivocal. The disease is usually portrayed as being of sporadic occurrence; although this conception is deeply rooted in medical opinion, it is open to question. To obtain an exact measure of the incidence of fatal pulmonary embolism in the general population, two conditions must be fulfilled: the evaluation must be based on autopsy examinations and a high percentage of the deaths in a given community over a period of years must be examined