Eight patients with upper extremity deep-vein thrombosis were treated with thrombolytic agents. The role of a compression syndrome of the costo-clavicular space (found in 5 out of 7 cases) as a probably thrombogenetic factor is discussed. The complications of the therapy were considerable, despite frequent laboratory controls. In one thrombosis of more than 6 months' standing the treatment was ineffective. In the other 7 cases the early clinical results were good. At follow-up 14 to 57 months after thrombolytic therapy, 5 out of 7 cases had residual symptoms (rethrombosis in 2 cases). This may be due to the fact that the compression syndrome was not initially treated, with resultant persistence of the chronic trauma to the vein. Better results can be expected from fibrinolytic therapy in combination with surgical correction of any anatomical narrowing.