Temporary clipping on parent artery is widely accepted as a useful method to prevent intraoperative aneurysmal rupture, to dissect the aneurysm safely, and to obtain the clear operation field during intraoperative aneyrysm rupture. However, the exact role and adequate technique of the temporary clipping has yet to be determined. The authors performed an experimental study to investigate the effect of temporary clipping on intra-aneurysmal pressure. The experimental aneurysms, using side-to-side anastomosis between common carotid artery and the jugular vein, were made in 24 rabbits. The intra-aneurysmal pressure was monitored through a catheter inserted in the aneurysm. The intra-aneurysmal pressure was significantly decreased to 31.8+/-4.39mmHg after temporary clipping on the proximal common carotid artery(p<.05). On the contrary, intra-aneurysmal pressure was increased to 73.3+/-4.39mmHg after the distal parent temporary clipping. In case of the temporary clipping on both proximal and distal parent artery, the intra-aneurysmal pressure was markedly increased to 81. 0+/-11.7mmHg(p=0.0036 on t-test). In conclusion, the temporary clipping on the parent artery should be performed only on the proximal site of the aneurysm. Temporary clipping on both proximal and distal site would be rather dangerous since it causes sharp increase in intra-aneurysmal pressure during the clipping of aneurysm itself.