Legionella is a pathogenic bacteria associated to aquatic habit of natural and artificial environments. Clinical cases of legionellosis have been reported in Korea but there is a lack of information about the incidence of this bacterium on environmental sources. Thus, we investigated the contamination of Legionella on water supply systems in Gwangju, Korea, including cooling towers, public baths, hospitals and fountains. Legionella spp. were detected from 81 samples (16.9%) out of 480 samples collected and the major species of Legionella isolates was identified to L. pneumophila serogroup (sg) 1 (n=33). The result of PFGE pattern analysis for L. pneumophila sg 1 isolates was discriminated into 11 pulsotypes. In dendrogram of PFGE, the clusters of isolates from cooling tower were quite different from those derived from hot water system of public bath. Surveillance for 4 sentinel public baths showed that their water supply systems had been contaminated with Legionella spp. and L. pneumophila sg 5 or sg 6 was the major isolate. The similarity of its PFGE patterns was 92.3%, 96.6%, respectively. Thus, PFGE may be a useful tool in molecular epidemiology studies, and the monitor and control for water supply systems of public utilizing facilities will be able to provide a resolution for the reduction of Legionella infection.