This experiment was carried out to evaluate the sanitary quality of ground water in Pusan area(see Fig. 1). One hundred and thirty two water samples were collected from the 11 stations from October 1981 to Sept ember 1982. To evaluate the sanitary quality, coliform group, fecal coliform, viable cell count and composition of coliform group by IMViC reaction were observed. The median value of coliform group MPN of the samples were 59/100 ml in Udong and Daesindong, 68/100 ml in Suyeong, Yeonsandong and Sungjigog, 43/100 ml in Jenpodong and Mangmidong, 33/100 ml in Yeongdo and Dongrae, and 13.3/100 ml in Gammandong. Geometric mean of fecal coliform MPM was 4.1/100ml in Udong, 8.6/100 ml in Suyeong, 8.1/100 ml in Jenpodong, 6.1/100 ml in Daesindong and Dongrae, 8.7/100 ml in Yeongdo, 7.1/100 ml in Mangmidong, 6.5/100 ml in Yeonsandong, 9.1/100 ml in Sungjigog, 3.0/100 ml in Gammandong and 7.6/100 ml in Gupo. The seasonal difference of total coliform showed much more contamination in June or July when there were more climers than in December though it was caused by the rise of loafer temperature. With 50 percentile of total coliform MPN July was about 30 times higher than December for July was 163.5/100 ml and December 5.3/100 ml, Particularly, June was about 1.3 times higher than July in contamination because of a sudden increase of people using it. Composition of coliform was $7.64\%$ Escherichia coli, group, $42.86\%$ Citrobacter freundii group, $16.78\%$ Klebsiella aerogenes group and $32.72\%$ others. Plate count of samples was varied from 48 to $4.4{ imes10}^2/ml$ during the study period.