A polymerase chain reaction for the rapid and specific detection of Mycobacterium tuberculosis has been used and evaluated for clinical applicability. Two oligonucleotide primers derived from the nucleotide sequence of a immunogenic protein MPB 64 amplified DNA from M. tuberculosis and M. bovis. No amplification was observed from any of ten different mycobacterial strains. A total of 126 clinical samples were amplified and tested by both dot blot hybridization and restriction enzyme analysis. M. tuberculosis was detected by PCR in 38 smear and 42 culture positive cases An additional 16 culture negative specimens mere PCR positive yielding an overall M. tuberculosis positivity rate of 46.0% (58/126) compared to 33.3% (42/126) by culture. The superior sensitivity of PCR to culture was more evident in non-pulmonary cases where PCR picked up 10 cases in addition to 6 culture positives out of 46 specimens. On the other hand, out of 80 pulmonary specimens only 6 cases in addition to 36 culture positives mere picked up by PCR. The specificity of PCR was confirmed with dot blot hybridization and restriction enzyme analysis. This study corroborates that PCR offers a more sensitive and rapid alternative for the detection of M. tuberculosis to culture, and that it can be used in uncultured clinical specicimens.