We use CDDP and have compared the semiselective intraarterial infusion (ia group) with intravenous infusion (i.v. group) by measuring levels of the administered drug in blood and the abdominal organ tissues. In portal blood, the ia group showed a significant increase compared with the i.v. group. The patient tissue level was compared between the two groups. Higher levels were obtained in the peritoneum in the ia group. These results suggest that semiselective intraarterial infusion therapy is effective in peritoneal dissemination.