A study was carried out to investigate the sanitary condition of 107 wells in Jungil Ri, Kyunggi province and Daeso Ri, Choongbuck province, from July 1, to August 30, 1975. In this study, coliform groups were examined by the membrane filter method as well as general sanitary condition, pH value, ammonia nitrogen, hardness and water temperature. The following results were obtained: 1. Average value of general sanitary condition in the wells were 15$circ$C in temperature, pH 6.4, hardness 124ppm and Cl ion 34ppm. 2. Coliform group was positive at all out of 30 open wells and 33 out of 45 pumped wells, while only 7 out of 32 tap water in the simple typed water supply system showed the evidence of coliform groups. 3. The positive rate of ammonia nitrogen revealed 13% out of 107 wells and that of nitrite nitrogen was 36.4% and 6 wells rate of 5.6% were ammonia nitrogen and nitrite nitrogen positive at same time. 4. Colflorin group positive of 32 tap water in the simple typed water supply system 3(27%) out of 11 samples with no residual chlorine, 3(17%) out of 17 with 0.1 to 0.5ppm, 1 out of 3 with 0.6 to 1.0 ppm and none out of 1 with 1.1 to 1.5 ppm.