OBJECTIVE To determine the role of ultrasonography (US) and computed tomography (CT) in the evaluation of ascites etiology. METHODS From 2000-2006, patients admitted to the Radiology Department, Uludag University Medical School Hospital, Bursa, Turkey, were studied to determine the etiology of ascites, or those in whom ascites was determined during the course of other investigations were evaluated using US and CT. Existence of septa-debris, accompanying organ pathology, omental involvement, intestinal wall thickening, peritoneal implant, lymph node, diameter of portal vein, thickening of gall bladder wall, pleural effusion, collateral vascular structure, and cavernous transformation were also investigated. RESULTS A total of 30 cases were included. Causes were determined to be malignant in 15 (50%) cases and 15 (50%) benign. The US was significantly superior to CT in the evaluation of gall bladder thickening. Omental thickening, thickening of intestinal wall, and peritoneal implant development were seen significantly more frequently in malignant compared to benign cases, while thickening of the gall bladder wall was seen more frequently in benign cases. Ascites density of malignant cases detected in slices without contrast was higher than in benign cases. The probability of malignancy was 98% when omental thickening, thickening of intestinal wall, and peritoneal implant were present together in the same case. CONCLUSIONS Although CT and US may help to evaluate ascites, however, the differential diagnosis of ascites etiology remains a challenge.