Four patients suffering from malignant ascites were treated with the following method: peritoneal lavage and consequent injection of Mitomycin-C (20 mg/body surface m2) was performed for six hours via a catheter put into the peritoneal cavity according to Seldinger's method. One patient died three weeks later because of involvement of other organs by the disease. The other patients have been followed-up ever since for 7, 4 and 3 months now. In their case there was no need for repeated intraperitoneal chemotherapy. There were no side-effects nor complications detected.