A retrospective study of autopsy-verified fatal pulmonary embolism at a department of infectious diseases was carried out, covering a four-year period (1980-83). During that time 8 646 patients were hospitalized at the department and 221 patients died. In addition, 103 patients died within 30 days of discharge from the department. Pulmonary embolism was found at autopsy in 38 cases (autopsy rate 78%). In 16 of these patients, acute pulmonary embolism was a major contributing cause of death, otherwise the prognosis would have been favourable. All 16 patients were over 55 years old and all but one were over 65 years old. The incidence of hospital-acquired clinically relevant autopsy-verified fatal pulmonary embolism in these age groups was 0.4 and 0.5%, respectively. In patients with respiratory tract infections, the incidence was 0.7 and 0.8% in the respective age groups.