The study was done to evaluate the ADA activity in the diagnosis of pulmonary tuberculosis and its relationship with clinical, radiological and laboratory parameters. The study was carried out on 142 patients suspected from various pulmonary disorders from July 2008 to January 2009. Forty five normal healthy individuals were included as control subjects for ADA evaluation. Four groups of patients namely A (0-20 yrs), B (21-40), C (41-60) and D (≥ 61 yrs) were formed and diagnosis was based on the x-ray Chest, Mantoux test, ESR, spu-tum AFB and Serum ADA level. The Sensitivity of various tests against ADA was done. In the diagnosis of Pulmonary tuberculosis, serum ADA showed high percent positivity of 88% followed by chest x-ray (76%), ESR (72%), sputum AFB (63%) and Mantoux Test (61%).Significantly high serum ADA level was reported in pulmonary tuberculosis cases compared to non tubercular pulmonary diseases. Sputum AFB negative pulmonary tuber-culosis cases have also shown elevated level of serum ADA at par with sputum AFB positive cases. In the present study serum ADA level in control group was 15.3 ± 0.23 U/L and cut off value was 33 U/L for diagnosis of pulmonary tuberculosis. As determination of ADA is not costly or time consuming, should be done routinely, particu-larly if the diagnosis of tuberculosis is in doubt, clinically suggestive but sputum AFB nega-tive cases and also to differentiate pulmonary tuberculosis from non tubercular pulmonary diseases.