The results of treatment of pulmonary embolism with heparin (n = 34), streptokinase (n = 28) or embolectomy (n = 25) are presented. The treatment groups represented different degrees of embolization with acute embolic scores (possible maximum: 20, mean +/- SD): 5 +/- 4, 9 +/- 3 and 13 +/- 3, respectively (p less than 0.0001). The post-treatment embolic score (mean +/- SD) for patients with acute massive central emboli (score greater than or equal to 9) was: 6 +/- 4 (n = 7) and 3 +/- 2 (n = 15) in the streptokinase and embolectomy groups, respectively, (p less than 0.01). The hospital mortality was 6% (n = 2), 21% (n = 6) and 20% (n = 5) in the heparin, streptokinase and embolectomy groups, respectively (p less than 0.05). The 5-year cumulative survival (+/- SE) was 68% +/- 10, 64% +/- 10 and 80% +/- 8, respectively (p: NS). The relative survival (hospital and late deaths, observed/expected) stratified according to acute embolic score showed the best results in the embolectomy group. Systolic pulmonary artery pressure greater than 60 mmHg was found in cases with a duration of symptoms greater than 7 days and/or with greater than or equal to 25 anamnestic recurrent embolic episodes before diagnosis, indicative of a gradual increase in pulmonary artery pressure and of partly organized non-lyseable emboli. Embolectomy carried a low risk of complications (8% with cerebral reduction). Streptokinase treatment was associated with serious complications (18% with cerebral reduction/fatal hemorrhage). Pulmonary embolectomy should be recommended in all cases with emboli in the main branches of the pulmonary artery.(ABSTRACT TRUNCATED AT 250 WORDS)