Malignant ascites is a manifestation of advanced malignant disease that is associated with significant morbidity. Mainstays of treatment include diuretics and recurrent large volume paracentesis. Although lymphatic obstruction has been considered the major pathophysiologic mechanism behind its formation, recent evidence suggests that immune modulators, vascular permeability factors, and metalloproteinases are contributing significantly to the process. These new observations offer the opportunity for development of new, more targeted therapies for the treatment of malignant ascites. This article uses a clinical case to highlight the problem, then reviews these new concepts in the pathophysiology of malignant ascites formation. The diagnosis and management of this challenging medical problem are subsequently discussed, with emphasis on how these new pathophysiologic insights are being applied to the development of novel therapies that may soon change how we manage this troubling clinical condition.