OBJECTIVE: The purpose of this study is to evaluate the feasibility of neuronavigation system for side selection of pterional approach in anterior type anterior communicating aneurysm. METHODS: Forty six anterior type aneurysms were evaluated with neuronavigation system based on computed tomography angiography from October 2005 to September 2008. According to neuronavigation system images the approach were subdivided into two groups. The approach in open standing group defined as the craniotomy was done in the A2 of the approach side located more posteriorly than the contralateral A2. The approach in closed standing group was defined as craniotomy was done in the ipsilateral A2 located more anteriorly than the contralateral A2. We analyzed operation time, premature rupture rate, temporary clipping time, perforator injury on postoperative CT scan and Glasgow outcome scale (GOS) of two groups. RESULTS: Thirty-three cases of approaches in open standing group and thirteen cases of approaches in closed standing group were evaluated. In operation time, premature rupture rate, temporary clipping time and GOS, no significant difference was observed between approaches in closed standing group and open standing group. But, in closed standing group, the perforator injury on CT scan was occurred more frequently than open standing group (p=0.001) in postoperative 7 days. CONCLUSION: With the neuronavigation system, three dimensional angiographic images were reconstructed by the operator and actively used to side selection of pterional approach for the aneurysm neck clipping. The perforator injury could be avoided with this policy.