This study was carried out to identify the source of water pollution in Naktong River through a study on indicator organisms such as fecal coliform and fecal streptococci from August, 1989 to February, 1990. The ratios of fecal coliform to fecal streptococci were high at the stations with heavy loads of human activities, and low with heavy loads of the animal activities. By performing the cluster analysis, eight major clusters were found from the 100 isolates of Nov., 1989, and eleven clusters from the 150 isolates of Feb., 1990. These clusters were identified in the following dominant order; Streptococcus faecalis, S. faecium, S. avium, S. bovis, S. durans, and S. equinus. Human fecal streptococci were predominant throughout the all investigated stations, and animal fecal streptococci were also found.