Cerebral vascularization by omental transposition or transplantation to the brain has been applied in experimental and clinical cerebral ischemia. However, in these operative procedures, it has not been discussed whether arachnoid dissection would produce significant benefit in cerebral vascularization. The purpose of this experiment is to observe the effect of arachnoid dissection upon cerebral vascularization in omental transposition to the brain. Forty healthy adult cats underwent partial craniectomy with dural opening and were divided into four experimental groups; Group 1-control group, Group 2-temporal muscle covering over the brain surface, Group 3-omental transposition to the brain surface and Group 4-omental transposition with arachnoid dissection. After 3 weeks of clinical observation on the occurrence of convulsive seizures, animals were subjected to permanent occlusion of middle cerebral artery by transorbital approach. For 24 hours, neurologic deficits were checked and then animals were sacrificed to evaluate the size of cerebral infarction. The results were as follows: 1) Convulsive seizures were observed in 2 cases among all the animals, but there was no statistically significant difference in the occurrence rate among each group. 2) Animals in groups of omental transposition revealed mild neurologic deficits, as compared to those in the control group and the group of temporal muscle covering. 3) There was no statistically significant difference in the size of cerebral infarction between the control group and the group of temporal muscle covering. But in groups of omental transposition, the size of infarction was remarkably small as compared to the control group and the group of temporal muscle covering (P<0.05). 4) Of the two groups of omental transposition, the group of arachnoid dissection showed smaller size of cerebral infarction (P<0.05). 5) There was a tendency that the infarcted area enlarged progressively as neurologic deficits were severely impaired, but the difference was not statistically significant. 6) Cerebral vascularization was most effectively produced in the group of omental transposition with arachnoid dissection.