Various factors using cell lines can effect kinds and frequencies of infectious viruses obtained in the detection tests on various water samples. We tried to find out technical problems for the maximum virus isolations from water samples and characterize the virus isolates from waters in nature and in various purification stages. Fourteen viruses were isolated from 169 water samples by virus monitoring protocol for the information collection requirements rule, US EPA. The morphological changes caused by viruses and mycoplasma infections were compared with for increasing the specificity of tests employed. Cytopathic effects of slow growing viruses were found very similar with those by toxic effects in water samples and mycoplasma infections. Five of 6 stream water samples tested (83.33%) showed virus contaminations with the range of 1.03 to 5.75 MPNs/100 liter. Eight of 24 source water samples (33.35%) showed viral contaminations. One water sample of 24 water samples during precipitation stages was shown to include infectious viruses. It was confirmed that infectious viruses were significantly decreased by purification stages from streams. The titers ($TCID_{50}$) of virus isolates were ranged as $10^{-6.8}{sim}10^{-6.925}/ml$. The virus isolates were identified by immune fluorescent antibody (IFA) method using virus specific immune sera and serotyped using serotype specific reference sera. Of 14 virus isolates, 7 samples were identified as poliovirus and the other 7 were identified as coxsakie virus. Of 7 polioviruses, one was serotyped as type I, 3 viruses as type II and another 3 as type III. Conclusively, BGM cell lines must be free of mycoplasma for the strict examination of infectious viruses in water and highly sensitive for mainly enteroviruses. In addition, most of infectious viruses showing typical cytopathic effect from water samples were confirmed as coxsackie B and live attenuated vaccine strains of 3 polio types when BGM cells were used for virus isolations.