The presence of intracoronary thrombus in acute coronary syndrome is associated with the increased risk of abrupt thrombotic closure, distal embolization and no reflow phenomenon after coronary intervention. Systemic or intracoronary administration of thrombolytic agent produces a systemic fibrinolytic state and/or requires prolonged drug infusion. The purpose of the present study was to assess the effects of local urokinase (UK) delivery on the intracoronary thrombus. We analyzed 28 patients (59.2+/-8.6 year; 18 male, 10 female) with acute coronary syndrome and angiographic feature of intracoronary thrombus, and divided into four groups according to the methods of UK administration. Thirteen patients (Group A), who developed filling defects after coronary intervention and received 500,000 units of intracoronary UK. Five patients (Group B), who developed total thrombotic occlusion immediately after coronary intervention, and were treated by 500,000 units of UK. Four patients (Group C) had definitive intracoronary thrombus and 500,000 units of intracoronary UK was administered before interventions. Six patients (Group D) had definitive intracoronary thrombus and local urokinase delivery was performed using the Dispatch Catheter at the lesion site for 5 minutes with an infusion rate of 1 ml/min. Thrombus score (TS) and Thrombolysis In Myocardial Infarction (TIMI) flow were analyzed according to different UK therapeutic modalities. In Group A, TS was changed from 2.6+/-0.5 to 2.3+/-0.7 after intracoronary UK (p=0.25) and TIMI flow increased from 1.07+/-0.9 to 2.0+/-0.7 (P=0.01). In Group B, TS was changed from 3.0+/-0.0 to 2.40+/-0.48 (P=0.08) after intracoronary UK and TIMI flow increased from grade 0.80+/-0.32 to 1.80+/-0.32 (P=0.02). In Group C, TS was changed from 3.00+/-0.0 to 2.66+/-0.4 (P=0.42) and TIMI flow from 1.66+/-0.4 to 2.00+/-0.7 (P=0.42). In Group D, TS was decreased from 2.20+/-0.55 to 0.30+/-0.44 (p<0.01) and TIMI flow increased from 1.83+/-0.55 to 2.66+/-0.44 (P=0.02). Local urokinase delivery in thrombus-burden coronary lesion is an effective method obtaining successful thrombolysis and improving coronary blood flow.