The ultimate goal in microvascular surgery is to achieve improved patency rates while reducing complications of systemic antithrombotic agents. Using a described model of microarterial thrombosis, the antithrombotic effects of oral aspirin (ASA) were assessed in rats. ASA-treated animals (30 mg/kg orally) exhibited significantly prolonged mean bleeding times 1 h and 24 h after dosing when compared to controls (p < 0.01). Platelet aggregation profiles also displayed an inhibition of platelet aggregation in the ASA group relative to controls. In the thrombosis model, however, patency rates were significantly improved at 20 min, but all vessels were thrombosed at 24 h.