We evaluated the usefulness of a Nested PCR method for detecting Legionella pneumophila. This method resulted in L. pneumophila specific detection as far as we evaluated. The first and second step PCR achieved the sensitivity as small as 10 pg and 10 fg of the target DNA, respectively. In the detection from Legionella seeded sputa, the method could detect 0.1 cfu/ml of the bacteria, and it took about 12 hours to detect the target DNA. We demonstrated that the Nested PCR method was superior in sensitivity and rapidity for isolation of the bacteria to the conventional using low pH treatment and selective media for Legionella.