A simple method(TET-boiling method) was used to treat 106 sputum samples compared with the typical phenolchloroform extraction of DNA. They yielded similar positive rates(44.3% vs 46.2%) of polymerase chain reaction(PCR), while nested PCR had a much higher one(72.6%) with the greatest difference from those with smear-negative and culture-negative results.Using purified DNA of Mycobacterium tuberculosis,we also determined the sensitivity(50fg) of nested PCR,which was 100 times as sensitive as PCR. But it didn't affect the specificity of PCR. PCR and nested PCR were all negative in 21 nontuberculous sputum samples. We conclude that the TET-boiling method is a simple and effective DNA extraction procedure,and it should be combined with nested PCR in detecting samples with very small amount of bacteria.