A 37-year-old female presented with a 2-month history of abdominal distention. Omentum masses with massive ascites were found and ovarian cancer with peritoneal carcinomatosis was suspected. Her serum CA-125 level was over 500 U/ml before therapy. Tuberculous peritonitis was diagnosed via peritoneal biopsy. The serum CA-125 level returned to normal after antituberculous therapy. Elevated serum CA-125 does not always indicate ovarian malignancy. This tumor marker may be used to monitor the disease activity in non-neoplastic ascitic states.