BACKGROUND Chylous ascites is the accumulation of triglyceride-rich, free, milk-like peritoneal fluid caused by the presence of intestinal lymph in the abdominal cavity. Primary chylous ascites is uncommon. We present our experience in the diagnosis and treatment of this condition. METHODS Twelve patients (7 adults, 5 children) affected by primary chylous ascites were studied. Diagnostic investigations included abdominal sonography scans, lymphoscintigraphy, and lymphography combined with computed tomography (CT) with intravenous and intralymphatic lipid-soluble contrast, and laparoscopy. Magnetic resonance imaging was used when lymphography and lymphatic CT were not able to define the dysplasia well, or in the presence of lymphatic dilatation. Surgical treatment included laparoscopy (12/12), drainage of ascites (12/12), the search for and treatment of abdominal and retroperitoneal chylous leaks (12/12), exeresis of lymphodysplastic tissues (12/12), ligation of incompetent lymph vessels (9/12), carbon dioxide laser treatment (cut and welding effects) of the dilated lymph vessels using an operating microscope for magnification (9/12), and chylovenous and lymphovenous microsurgical shunts (7/12). RESULTS Eight patients did not have a relapse of the ascites, and three patients had a persistence of a small quantity of ascites with no protein imbalance. Postoperative lymphoscintigraphy in seven patients confirmed better lymph flow and less lymph reflux. Median follow-up was 5 years (range, 3 to 7 years). We observed early relapse of chylous ascites in only one case that required a peritoneal-jugular shunt and led to good outcome. CONCLUSIONS Primary chylous ascites is closely correlated to lymphatic-lymphonodal dysplasia that does not involve a single visceral district alone. Medical preoperative treatment played an essential role in the global management of this complex pathology. We demonstrated that the use of laparoscopy is remarkably advantageous for confirming diagnosis, for draining the ascites, and for evaluating the extension of the dysplasia. Our diagnostic work-up provided us with an exact diagnostic assessment and allowed us to plan a precise surgical approach.