Intra-arterial thrombolysis (IAT) was used as first-line treatment for 100 occlusions causing acute, subacute or chronic ischaemia. Streptokinase was used in 90 cases and tissue plasminogen activator in the remaining ten. Complete lysis, as determined radiologically, was achieved in 55 per cent of cases and partial lysis in 20 per cent. Lysis was more effective the earlier it was used. Major complications occurred in seven cases: five patients suffered major haemorrhage, two of whom died, and two had haemorrhagic cerebrovascular accidents. Of the patients with complete or partial clearance of thrombosis, 19 had no underlying apparent cause, 23 underwent angioplasty and 15 had an operation. The 1-year patency rate following complete lysis was 58 per cent. The 1-year patency rate after successful treatment commencing within 1 week of symptoms starting was 71 per cent, compared with 36 per cent for later treatment. Aortofemoral bifurcation grafts were cleared in three of five cases and all remain patent. Eight popliteal aneurysms were demonstrated by IAT and were ligated and bypassed; all these grafts remained patent at follow-up. IAT is less effective in chronic than acute occlusion. It should be reserved for patients in whom the occlusion is of short duration or for those with a thrombosed aortofemoral bifurcation graft or popliteal aneurysm.