Eleven patients with advanced ovarian carcinoma who had large quantities of ascites during the course of previous chemotherapy were tested with intraperitoneal injections of tranexamic acid, followed by combination chemotherapy. A 4-g dose of tranexamic acid was administered intraperitoneally every day for at least 2 weeks. Seven out of 11 patients (63.6%) showed changes from positive to negative in Papanicolaou smears of the ascitic fluid after treatment with tranexamic acid. A marked reduction of ascitic fluids was observed in 4 of 11 patients (36.4%). If 2 cases with partial reduction of ascites are included, the response rate improved to 54.5%. Median survival time after initiation of treatment with tranexamic acid was significantly longer in patients with good response to tranexamic acid than in patients with poor response. Proliferation of cells in cultures established from ovarian cancer tissue of a patient with good response to tranexamic acid was inhibited at all concentrations of tranexamic acid used in this study, in contrast to non-inhibition of similar cells cultured from a patient with poor response, at any concentration of tranexamic acid. These results suggest that treatment with tranexamic acid suppresses malignant cells in the ascites, followed by reduction of ascites themselves, and an improvement in the response rate to subsequent chemotherapy.