Three methods in the diagnosis and treatment of tuberculosis have been compared in this study. Serum adenosine deaminase activities of patients with tuberculosis was compared with those of control groups with (+) and (-) PPD (purified protein derivative) results and were found to be higher than the controls. Within the controls the PPD (+) group displayed higher adenosine deaminase activities in comparison to the PPD (-) group. All patients had growth of B. Tuberculosis in the culture medium and all but one had positive polymerase chain reaction (PCR) results. Control patients were negative for culture and PCR. The sensitivity of ADA (adenosine deaminase) assay was 91.7% and specificity was 94.5%, whereas PCR had a sensitivity of 95.8% and a specificity of 100%. The ADA assay may be used in adjunction with other methods in the follow-up of tuberculosis with high sensitivity, specificity, and ease in applicability and specimen collection. J. Clin. Lab. Anal. 13:209-212, 1999. (C) 1999 Wiley-Liss, Inc.