Background: Various serum markers have been shown to be helpful in diagnosing tubercular infection, but none has been proven to be specific. The present study was undertaken to ascertain the role of serum cancer antigen (CA) -125 in diagnosing and monitoring therapeutic response in abdominal tuberculosis.Methods: Fifty diagnosed cases of abdominal tuberculosis and equal number of controls were included in the study. All the patients underwent clinical, radiological and hematological examination. Twenty-two patients had acute presentation and underwent laparotomy and twenty-eight patients had a chronic presentation and were managed conservatively. Biopsy was taken in all patients undergoing laparotomy. Serial measurement of serum levels of CA-125 were done at 0, 3 and 6 months in all the patients.Results: The CA-125 levels were significantly higher in tuberculosis patients than in control group (PPV 95.74% at 0 month). It was also observed that the levels correlated significantly with the disease activity (sensitivity 90 percent, specificity 96 percent) and return to normal level with the treatment given. It was shown that sensitivity reduced to 12 percent and 6 percent at 3 months and 6 months respectively after completion of treatment. The specificity however remained unchanged.Conclusions: The measurement of CA-125 may be a valuable parameter in diagnosing and determination of disease activity in abdominal tuberculosis.