This investigation was conducted to investigate the chemical characteristics and coliform group contamination of the household open wells, public open wells, and pumped wells in eight Dongs in the vicinity of Cheong-Ju City where the municipal water supply system is not available, and of the simple water supply system established in five Myuns of Cheong-LYon Gun. The quality of the sample waters is characterized by the average pH, 6.6; chloride ion, 51.8ppm; hardness, 112.0ppm; the number of coliform group, 63.2; percentage of NH₄^+-N positive, 14.7% ; percentage of NO₂^--N positive, 29%. The percentages of coliform group positive responses of the drinking Beaters from pumped wells, household open wells, public open wells, and simple water supply systems are 60.8, 66. 7, 96 and 26%, respectively. The average number of coliform group was 41 to 80 per 100㎖ in all types of wells. The percentage of the coliform group positive response in the wells where the concentration of chloride ion ie lower than 30ppm, is 27.7%; whereas it increase considerably with the increased concentration of chloride ion. The percentage of the coliform group response in the wells where the detection of NH₄^+-N and NO₂^--N is not consistent, is 79∼80%; whereas it is 100% in the samples where both types of nitrogen were detected. The water from the simple water supply system showed the colifrom group positive response in the case where the concentration of the residual chlorine is lower than 0.5ppm, whereas it showed the negative response in the case where it is higher than 0.5ppm.