Abstract: Three methods were evaluated:（1）an assay of amplification for a 245 bp segment derived from therepetitive DNA IS986 specific for mycobacterium tuberculosis cornplex was developed by using polymerasechain reaction（PCR）,（2）a sandwiched enzvme linked imnlunosorbant assay（ELISA）was developed by usingmonoclonal antibody（Mab）TB15-C3 that recognized specific antigenic determinant of mycobacterium tuber-culosis, and （3）a conventional acid-fast stain,Ten strains of acid-fast mvcobacteria and 2 strains of non-my-cobacteria were tested.The specific PCR product was obtained only from mycobacterium tuberculosis com-plex.Tests for M,tuberculosis and BCG,M.avium and M.scrofulaceum were positive by Mab-ELISA anal-vsis.All strains of acid-fast mycobacteria were positive by conventional acid-fast stain.The sensitivity of PCR in the detection of M. tuberculosis genomic DNA and bacteria suspension was lpg,corresponding to 100 viable bacteria cells.The sensitivity of detection of PPD by Mab-ELISA was 15ng/ml,and the sensitivity of conventional acid-fast stain was 10￣4 viable bacteria cells.One hundred and thir-ty-eight clinical specimens from patients with tuberculosis were examined by the three methods.The positivi-ty rate of PCR was higher than that of conventional acid-fast stain（P＜0.05）.The positivity rate of Mab-ELISA in detection of specific antigenic determinant was much higher than that of both conventional acid-faststain and PCR（P＜0.01）.The false positivity rate of Mab-ELISA was not remarkably higher than that ofPCR （P＞0.05）.Our results suggest that PCR and Mab-ELISA appear to be specific,sensitive and rapidtechniques for the diagnosis of tuberculosis.