Malignant ascites occurs in association with a variety of neoplasms. It is a frequent cause of morbidity and presents significant problems for which there are no clear management guidelines. In this article we discuss various modalities which are available including diuretic therapy, paracentesis, peritoneovenous shunts and intraperitoneal chemotherapy. There are no randomized trials of diuretic drugs to assess their efficacy in malignant ascites. Phase II data suggest that they are effective in approximately one-third of patients with malignancy, and their efficacy may be determined by plasma renin/aldosterone concentrations. Paracentesis provides relief in up to 90% of patients; because of varying reports of hypovolaemia, some advocate simultaneous intravenous fluid infusion. Permanent percutaneous drains may prevent the need for repeated paracentesis, although there is potential for infection. A peritoneovenous shunt also prevents the need for repeated paracenteses, whilst maintaining normal serum albumin concentrations. Blockage occurs in 25% of shunts, which are contraindicated in the presence of heavily bloodstained ascites because of the risk of occlusion. The preclinical and clinical experience with anti-angiogenic agents such as the matrix metalloproteinase inhibitors and the VEGF antagonists suggests that these agents may have a role in the treatment of malignant ascites. © 2003 The Royal College of Radiologists. Published by Elsevier Science Ltd. All rights reserved.