Aims: To evaluate an integrated cell culture (ICC)-multiplex-nested PCR using the buffalo green monkey kidney (BGMK) cells for the simultaneous detection of both enteroviruses and adenoviruses in surface water and tap water samples and optimize the procedure for more sensitive detection of virus showing no apparent cytopathic effect (CPE). Methods and Results: A total of 69 surface water and 50 tap water samples were analysed by the ICC-multiplex-nested PCR. All the PCRs were performed five times with a cell lysate from each flask after at least 2 weeks incubation. Forty-six surface water samples (66(.)7%) and 23 tap water samples (46(.)0%) exhibited CPE by the cell culture method. By using an ICC-multiplex- nested PCR, 53 surface water samples (76(.)8%) and 29 tap water samples (58(.)0%) were determined as containing infectious enteric viral particles. Conclusions: An ICC-PCR method with a long incubation time using BGMK cells enables the simultaneous detection of enteroviruses and adenoviruses from environmental water samples, including tap water, even with low numbers of viruses. Significance and Impact of the Study: A method capable of detecting small numbers of viral particles is necessary.