Behaviour of somatic and F-specific coliphages, as model viruses, in a full-scale slow sand filtration (SSF) treatment plant of Japan was investigated through enumeration with the conventional plaque-forming unit (PFU) and the real-time reverse transcription polymerase chain reaction (RRT-PCR). The results showed that in the effluent of SSF, concentration of coliphages decreased while Qβ phage, as a part of F-specific coliphages, was still detected by the RRT-PCR method. The detection of Qβ may indicate that F-specific RNA phages in the water were mainly derived from human faeces. Moreover, the practice of partial regeneration of the filters did not obviously affect the whole performance of the sand filters in removing coliphages and indicator bacteria (E.coli, total coliforms, general bacteria and heterotrophic bacteria). Furthermore, strong correlations were not obtained among all model viruses and indicator bacteria in the SSF effluent as well as the general water quality indices (turbidity, DOC and UV260). However, a relatively strong correlation was found existent between the indicator bacteria and particle numbers.