High-protein ascites in patients with the acquired immunodeficiency syndrome. Diseases of the liver or peritoneum resulting in ascites have been infrequently reported in patients with the acquired immunodeficiency syndrome. Since 1985, eight noncirrhotic patients with the acquired immunodeficiency syndrome presenting with new onset high-protein ascites have been evaluated. All but one patient had nondiagnostic paracentesis studies. Laparoscopy with biopsy of identified abnormalities or percutaneous omental biopsy were diagnostic in four patients. Non-Hodgkin's lymphoma was the cause in three patients, and disseminated cryptococcosis occurred in one patient. In the four other patients, chronic nonspecific peritonitis was found at laparoscopy; follow-up of these latter patients, including exploratory laparotomy in one patient and autopsy in two patients, disclosed no specific cause. Patients with the acquired immunodeficiency syndrome and high-protein ascites of uncertain etiology should undergo directed peritoneal evaluation as a potentially treatable disorder may be found. However, despite extensive evaluation, a subset of patients in whom no specific cause can be identified still remains. 