A case of a 32 years old woman with fever and exudative ascites is described. Tuberculous peritonitis was confirmed by abdominal laparoscopy, peritoneal biopsy and Lowënstein culture. A serum CA 125 level was 861 U/ml before therapy. The CA 125 level decreased a 30% after three weeks of antituberculous treatment. This tumor marker may be used to follow disease activity in tuberculous ascites.