Intra-arterial hepatic infusion chemotherapy combined with degradable starch microspheres (DSM) and mitomycin C (MMC) was performed for 9 patients with inoperable hepatic metastases from alimentary tract primary cancer. DSM, 45 +/- 5 micron in average diameter, produces temporary obstruction of arterial blood flow in the arterio-capillary bed and are subsequently degraded by serum amylase with T 1/2 of about 30 min. This intra-arterial treatment was repeated 2.3 times on the average. The average dose of DSM in a single infusion was 721 +/- 194 mg and the average total dose of MMC was 34.4 +/- 22.3 mg. Antitumor effects were evaluated in terms of tumor regression measured by CT scan and sonography. An objective tumor response was shown in 4/9 patients (44.4%): PR, 2/9; MR, 2/9. Elevated serum CEA levels of more than 3.0ng/ml were decreased in 7/8 patients (87.5%). Marked declines in the CEA level of more than 50% were observed in 4/8 patients (50%). Nausea and vomiting as well as abdominal pain were experienced in 8/21 treatments (38.1%) and 5/21 (23.8%), respectively. Furthermore, fever (2/21 : 9.5%), hepatic dysfunction (2/21 : 9.5%), and leukopenia (1/21 : 4.8%) were observed. All these side effects, however, were mild and transient. Thus, these results suggest that combined intra-arterial administration of DSM and MMC favorably enhances the antitumor efficacy of MMC.