A year-long survey of bacteriological water quality for Lake Eui-am in Kang- won Province, Korea, was conducted from June 1970 to May 1971. the purpose of this investigation was: 1) to determinate the seasonal prevalence of fecal pllution bacteria, such as coliforms, fecal coliforms and enterococci, in Lake Eui-am; 2) to correlate these findings with associated microbiological parameters; and 3) to interpret these results with respect to water quality and environmental health. The membrane filter techniques were used, for the determination of these bacteria.Densities of total coliforms, fecal coliforms and enterococci exhibited seasonal variations, the numers of these fecal pollution bacteria being high in summer and fall months in close possitive relation to the amount of rainfall, and being low winter and spring months. On the whole, the level of fecal pollution bacteria in Lake Eui-am is yet quite low There were not any evident correlation among the density of these pollution bacteria. The ratio of fecal coliforms to enterococci of the lake water varied from 0.01 to 4.25 with average of 1.47.