1. Studied on the quality of water Choong-ryang stream from Wangship-ri to Euijeong-bu during Summer season in 1969. 2. According to the change of water quality, the Choong-ryang stream might be divided into three areas. In the first area from Euijeong-bu (st.6) to near Chang-dong (st.5), the water quality is a little polluted that the value of DO is 7∼8 ppm, CI^- 16∼27ppm, COD 2.5∼9.5ppm, Alkalinity 15∼28ppm and Total hardness is 35∼55ppm. 3. In the second area from Choong-ryang brigde (st.4) to near Wangship-ri (st.3), the water quality is very polluted that the value of DO is low and the values Cl^-, COD, Alkality, Total hardness, SO₄^(-2) and NO₃-N are high. 4. In the third area from Wangship-ri (st. 3) to Han river (st.l), which contains sewage of Cheonggye stream, the water quality is seriously polluted that the value of DO is very low and the values of Cl^-, COD, Alkalinity, Total hardness. SO₄^(-2) and NO₃-N are very high. 5. The water quality of the first area belongs to the α and β-mesosaprobic zone, that of the second area belongs to the β-polysaprobic zone and that of the third area belongs to the α-polysaprobic zone.