This study was performed to improve the prognosis of unresectable (primary non-curative and recurrent) colorectal carcinoma by using pharmacokinetic modulating chemotherapy (PMC), a combination of oral UFT and continuous venous 5FU infusion. The subjects were 120 patients who were prospectively selected for this study. The patients selected PMC or alternative treatment. Fifty-six patients received PMC. The PMC group received 200-400 mg/body/ day UFT orally 5-7 days per week and 600 mg/m2/24 h 5FU infusion once a week. PMC markedly improved the median survival period (26.6 months vs. 9.2 months P<0.000001). This significant improvement as observed in unresectable primary colorectal carcinoma (P=0.0003), recurrent tumors (P<0.00001), local extension (P=0.01), lung metastases (P=0. 03), liver metastases (P=0.0001), and peritoneal seedings (P=0.02). One of 56 patients who received PMC developed grade 4 toxicity. PMC significantly improved the prognosis of unresectable colorectal carcinoma which has a low survival rate. PMC also indicated tolerable compliance and cost effectiveness.