The aim of this retrospective study was to assess pulmonary reperfusion by scintigraphy, the risks of recurrent embolism and of bleeding complications at the 7th day and 3rd month in 2 groups of patients admitted to hospital for massive pulmonary embolism without cardiogenic shock treated by intravenous thrombolysis (Group I) and by subcutaneous low molecular weight heparin (Group II) paired by Miller's index. The basal characteristics of the two groups, each comprising 31 patients, were comparable with respect to the severity of the pulmonary embolism with an average global scintigraphic defect of 40.6 +/- 13.5% in Group I and 39 +/- 13.7% in Group II. The scintigraphic changes at the 7th day were comparable with a relative improvement of 55 and 51% respectively and at 3 months of 74% in both groups. There was no significant difference in terms of recurrence of embolism (3 versus 0% at the 7th day and 3% in each group at 3 months) or of bleeding complications (13 and 10% at the 7th day and 10 and 6% at 3 months respectively). Low molecular weight heparin seems to be as effective as intravenous thrombolysis for the treatment of massive pulmonary embolism without shock. This result requires confirmation by a large scale prospective randomised trial.