A case of an inoperable recurrent retroperitoneal liposarcoma, histologically diagnosed as being a mixed myxoid type and a round cell type, which was treated by continuous intra-arterial infusion chemotherapy, is reported. The authors applied this treatment method using adriamycin and 5-FU via the feeding arteries, i.e., the superior and the inferior mesenteric arteries. The tumor showed remarkable regression with no severe complications, even though general chemotherapy using adriamycin proved to be ineffective. This infusion method was thus evaluated as highly effective.