Background: Glycoprotein IIb/IIIa receptor blocker is an important tool to inhibit platelet activation during percutaneous coronary intervention (PCI). However, the optimal dose of tirofiban has not been determined during PCI. Therefore, we evaluated the acute inhibitory effect of various doses of glycoprotein IIb/IIIa receptor blocker (GP IIb/IIIa blocker) on the platelet function during PCI. Methods: Since June to July 2003, 16 patients (mean ages, 63 짹 17 years [range, 48-81], 14 male) were enrolled in this study. Acute inhibitory effect was evaluated in a randomized protocol with 3 different GP IIb/IIIa blocker doses: current Reopro dose (0.25 mg/kg bolus and 0.125 關g/kg/min), current Tirofiban dose (TCD; 0.15 mg/kg bolus and 0.15 關g/kg/min continuous) and double bolus high Tirofiban dose (THD; 0.30 mg/kg bolus with 0.15 關g/kg/min continuous). Platelet function was measured by Ultegra Accumetric device before and 15 min, 1 hr and 3 hr after GP IIb/IIIa blocker infusion during PCI. Results: Data are as follows (Table, *p<0.05). Conclusions: Current dose of Reopro was not superior to tirofiban on acute platelet function inhibition during PCI. Further study is needed to prove this result.