Abstract: Objective: To examine the Willis circles of the patients with posterior circulation and no-posterior circulation transient ischemic attack(TIA) using the spiral CT angiography,and explore the correlation of Willis circle integrity with posterior circulation TIA.Methods: The cerebral vessels in 31 patients with posterior circulation TIA and 31 patients with no-posterior circulation TIA were analyzed using the spiral CT angiography.According to the results of examination,the Willis circles in all cases were divided into the complete,partial complete and incomplete circulation,respectively,and the variation of Willis circle was analyzed.Results: Different degree variation of Willis circles in two groups were found,and the incomplete Willis circles in patients with posterior circulation TIA were more.The difference between the complete and incomplete of posterior circulation in two groups was statistically significant(P<0.05),the difference between the complete and incomplete of anterior circulation in two groups was not statistically significant(P>0.05).Conclusions: The Willis circle integrity is correlation with the occurrence of posterior circulation TIA.