We examined the occurrence of brain infarction with hepatic arterial infusion chemotherapy for liver cancer. One hundred and eighty-one cases of hepatic arterial infusion chemotherapy were carried out for liver cancer patients in 4 hospitals associated with Osaka University 2nd Dept. of Surgery. These included metastatic (n = 103) and primary (n = 78) liver tumors. The medication was mainly 5-FU with/without CDDP and IFN. Catheters were inserted via the left subclavian artery in 106 cases and via the femoral artery in 75 cases. Among these patients, brain infarctions occurred in seven patients. Occlusions were found in the cerebellum (n = 3), thalamus (n = 1), brain stem (n = 1) and TIA (n = 2). All these patients had catheterization from the left subclavian artery. Furthermore, 64 patients of Ikeda Municipal Hospital were examined and analyzed for brain infarction, in order to eliminate the difference between facilities (all patients in Ikeda Municipal Hospital were catheterized via the left subclavian artery). Many more brain infarctions occurred in metastatic liver cancer patients than in primary liver cancer patients. The hemostasis function deteriorated in primary liver cancer patients, and is thought to be involved in the brain infarction. Six of seven cases of brain infarction occurred in vertebral artery supply area. It may be that the occurrence of brain infarction was related to the flow of the blood vessels.