We present the results of an enzyme-linked immunosorbent assay that detects serum antibodies to M. tuberculosis antigens. The patients sera were tested with two different antigens, one a M. tuberculosis H37Rv culture filtrate protein extract precipitated with ammonium sulfate (CFPE), and the second, a delipidized CFPE (CFPE-d). The results obtained with 52 clearly defined TBP patients was 0.50 +/- 0.16 (CFPE) and 0.38 +/- 0.11 (CFPE-d). We also tested 165 sera from patients hospitalized at the INER with a diagnosis of non-tuberculous pulmonary disease. In this patients the assay revealed 153 negative sera (CFPE = 0.053 +/- 0.01; CFPE-d 0 0.050 +/- 0.004) and 12 positive sera. Nine of these patients (CFPE = 0.38 +/- 0.08; CFPE-d = 0.32 +/- 0.09) had mycobacterias and the results of the remaining three were considered as false positive. TBP was excluded in all the 153 negative patients. The elimination of lipids in the CFPE did not alter the assay since the differences between CFPE and CFPE-d did not reach statistical significance. In non-tuberculous individuals the reactivity with mycobacterial lipids was poor and didn't induce false positive results. The assay we report can be useful in those patients with pulmonary disease where TBP has to be considered.