Three patients received intraperitoneal chemotherapy of low-dose CDDP for carcinomatous ascites due to gastric and colorectal carcinoma. Intraperitoneal injection of CDDP (30-50 mg) was given and the patients underwent systemic chemotherapy. As a result, the QOL of all patients was improved. Adverse effects of Grade 1 were observed in 1 case (nausea). This intraperitoneal chemotherapy seems to be safe and effective for ascites due to peritonitis carcinomatosa.