In view of ever rising water pollution problems of river in the vicinity of large urban communities, the author has made an investigation on the pollution of water sampled from Han River (Seoul area) and Nakdong River (Daegu city area) during the period from july to December, 1970. The water samples were taken twice a month during the study period of 6 months from 7 points (locations) along the main stream of Han River at Seoul city and 5 points of Nakdong River at Daegu city. The samples ware measured and analyzed in accordance with the recognized methods in the "Standard Methods or Examination of Water and waste" by American Public Health Association. The obtained results are as follows: I.Han River. 1. Average turbidity was 5.1 units ranging from 1 to 10 units and the turbidity of down stream was higher than that of the upper stream. 2. pH value showed slight alkalinity (mean ; 7.2) except Yunchang-Dong (6.9). 3. The mean value of Dissolved Oxygen contents (D.O) was 7.2 ppm (range of 3.4-10.5ppm). D.O of the upper stream (8.2 ppm. at Walker Hill boating place, 8.0 ppm. at the Gwangzang Bridge and Ddookdo) was higher than that of he downstream (5.6ppm. at Yunchang-Dong. 6.4ppm. at the 2nd Han River Bridge), and D.O in the winter season was higher than that in the summer season, respectively. 4. The mean value of the Biochemical Oxygen Demand (B.O.D.) was 28.3 ppm. (range of 6.2-64.8ppm). The mean value of B.O.D. was 48.7 ppm. at Yunchang-Dong. 42.3ppm. at the 2nd Han River Bridge, 34.0 ppm. at the 1st Han River bridge, 28.5 ppm. at the 3rd Han River Bridge, 19.2 ppm. at Dookdo, 13.2 ppm. at the Gwangzang Bridge, and 10.2 ppm. at the Walker Hill boating place in order of value. B.O.D. in July and August (35.6 and 34.5 ppm.) were the highest and that in November and December (18.6 and 21.2 ppm.) were the lowest. 5. Suspended Solids (SS) were from 15.0 to 667.0 ppm. with the mean of 222.1 ppm "Suspended Solids" of the water samples at Yunchang-Dong and the 2nd Han River Bridge were found to be 378.1 ppm. and 283.9 ppm. respectively which were higher than at the Gwangzang Bridge (134.1ppm.) and at Walker Hill boating place (79.3ppm). 6. Coliform colonies counting of the water samples ranged from 0-2, 500x10/100ml. with the mean value of 205.6x10/100ml. The most contaminated water sample by coliform were from the point of the 2nd Han River Bridge with 640.8x10/100ml while the lowest ones were from Walker Hill boating place with 17.2x10/100ml. There was also a seasonal variation in coliform contamination that is the higher in summer and the lower in winter. II. Nakdong River. 1. The mean value of turbidity was 2.3 units with range of 0 to 9.0 units. The highest point was at Geumho River (7.2 units). and the lowest point was at Gangzung and Moonsan (0.45 and 0.41 units). 2. The mean value of pH was 7.5 (range of 7.1-8.5) and highest point was Geunho River with 8.5. 3. The mean value of D.O was 8.1ppm. (range of 3.4-11.2 ppm.). D.O. of the upper stream showed higher value than that of the down stream, and the winter season than the summer season. 4. B.O.D. ranged from 2.6 to 57.0 ppm. (mean; 20.4 ppm.). The water sample at Geumho River showed the highest value (41.5ppm) while at Moonsan and Gangzung showed the lowest (4.6 and 4.7 ppm.). 5. The mean value of suspended solids was 48.7 ppm. (range of 4.0-182.0 ppm.). The highest month was July (63.7 ppm.) and August (62.1 ppm.) and the lowest month was October (37.0 ppm.) and December (24.4 ppm.). 6. The mean value of the coliform colonies was 22.7x10/100ml. (range of 0-243x10/100ml.). The highest number of the colonies was found in the sample water at the Whawon recreation area (50.5x10/100ml.) followed by the Geumho River (33.9x10/100ml;), the Goryung Bridge (28.3x10/100ml.), Gangzung(0.7x10/100ml), and Moonsan (0.6x10/100ml.).