The objective of this study was to evaluate the effect of hypertension on the use of thrombolytic therapy in patients with occluded synthetic peripheral bypass grafts. Thrombolysis with urokinase was performed in 44 cases of occluded lower extremity bypass grafts. The cases were divided into two groups: Group I consisted of patients currently being treated for hypertension. Group II consisted of patients without a history of hypertension. A comparison of pre- or intra-lytic data revealed that there was no significant difference in each group. Complications occurred in 15 (32.6%) out of 46 cases. There was no significant increase in complication when the risk factors were compared. In Group I, the one, two, and three year patency rates were 42.7%, 23.0%, and 7.7% and the limb salvage rates were 93.3%, 73.9%, and 73.9% for one, two, and three years respectively. The Group II patency rates were 70.6%, 41.6%, and 41.6% and the limb salvage rates were 94.1%, 86.9%, and 86.9%. The patency rate was significantly reduced when Group I was compared to Group II (p < 0.05). There was no statistically significant difference in limb salvage rates between Groups I and II. In conclusion, hypertension is one of the important risk factors that reduce the patency rate after thrombolytic therapy in patients with peripheral arterial bypass graft.