Thrombolytic therapy leads to more rapid dissolution of thrombi in severe pulmonary embolism than conventional heparin therapy but is considered with much reserve in elderly patients because of the risk of haemorrhage, which is thought to be potentially greater in these subjects. The object of this study was to assess the efficacy and safety of thrombolytic therapy in patients over 70 years of age with severe pulmonary embolism, compared with patients under 70 years of age with the same condition. Eighty-nine patients with severe pulmonary embolism (Miller score > 17/34) were prescribed thrombolytic therapy in the absence of a contraindication without taking age into consideration. Fifty-three were under 70 years of age (54 +/- 15; range: 18 to 70 years) and 36 were over 70 years of age (78 +/- 5; range: 71 to 88 years). Apart from age, there was no difference in the clinical presentation of the two groups. Thrombolytic therapy was initiated with streptokinase 100,000 IU/hr for twelve hours after an initial bolus of 250,000 IU or with urokinase or plasminogen tissue activator in cases with a contraindication to streptokinase. An uncomplicated course was observed in the same percentage of cases in the two groups. The Miller score and mean pulmonary pressures fell in the same way in the two groups. Three patients died during the hospital period, two aged under 70 (3.7%) and one over 7 years of age (2.7%). Major bleeding occurred in 3 subjects under 70 (5.6%) and 5 subjects over 70 (13.8%) (p = 0.29).(ABSTRACT TRUNCATED AT 250 WORDS)