Influences of human excrement on the water quality in Chungryang stream and Wangsuk stream were investigated three times during April 3 rd∼4 th, June 29 th∼30 th and September 6 th in 1984. Using coprosterol, cholesterol and urea as an index of fecal pollution, from the all sampling sites of both streams, it was detected fecal sterols but as a little amount. Therefore it was suggesting the pollution with human excrement from the stream basin. As a rule, the concentration of fecal. sterols in water of Chungryang stream was more higher than that of Wangsuk stream, moreover the concentration of fecal sterols in the water of Chungryang stream was showed wide variance in accordance with sampling sites. From the concentration of fecal sterols and the ratio of coprosterol to cholesterol, it guess Chungryang stream was severely contaminated with the waste water from the residental district near this stream basin. On the other hand, for the sake of the concentration and the ratio of these fecal sterols, it should guess that the pollution of small amount of coprosterol in the Wangsuk stream was mainly due to the waste water of ranchs near the stream basin.