Thrombolytic therapy has been used for treating patients suffering from a variety of clinical disorders including patients suffering from extensive venous and arterial thrombosis. This paper describes a combined approach to lytic therapy consisting of administration of small doses of streptokinase in combination with the infusion of plasminogen. The rationale for this approach is based on recent observations that additional plasminogen will be absorbed into preformed thrombi, rendering them more susceptible to lysis in the presence of activators. Forty-four patients who presented with symptoms and signs of acute or sub-acute deep vein thrombosis (DVT) confirmed by phlebography, were included in this study. Group I: 15 consecutive patients received an infusion of 600,000 units of SK dissolved in 50 ml of physiological saline over a period of half and hour. On the subsequent 4 days, a dose of 300,000 units was given twice daily. Group II: 29 consecutive patients received 60 to 90 mg of pretreated plasminogen dissolved in 50 ml of saline given intravenously over 30 min. and followed by same dosage regimen of SK. Blood samples were taken at varying intervals to assess changes in the haemostatic parameters. These were analysed for levels of alpha 2-antiplasmin, antithrombin III, fibrinogen, plasminogen, fibrinogen and degradation products, fibrinolytic activity and levels of activator complex. Findings observed will be presented. Phlebograms were performed before starting treatment and were repeated at the end of 5 days when the treatment had finished. In Group I--(15 patients)--thrombi remained virtually unchanged in 12 out of 15 patients receiving streptokinase infusion; in 3 (20%) there was partial but extensive lysis. In contrast, in Group II--(29 patients)--in 16 (55%) of 29 patients receiving plasminogen and streptokinase infusion, complete lysis of thrombi was obtained. Seven (24%) showed extensive clearance of venous tree while in remaining 6, thrombi virtually remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)