Hiroshima Environment and Health Association, Hiroshima 730Faucet-connected water purifiers with a filter consisting of activated carbon and hollow filament membrane, have recently become widely used at home. To examine the usefulness of this type of water purifier in the kitchen, microbial contamination, trihalomethanes and residual chlorine were used as indexes of filterability. Neither bacteria nor mold was detected in filtrated water at any time of use. However, slight bacterial contamination in the stagnant water of the filter was observed after 1 month of use and as well as bacteria, mold possessed of weak toxicity was detected after 8 months of use. After the water purifier had been fitted with a new filter, the values of trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane, bromoform and total trihalomethanes) were much lower than those in the unfiltered water, showing the effectiveness of filtration. This beneficial effect gradually decreased and had disappeared 2 months after the beginning of use. No residual chlorine could be detected in the filtrated water after 1 month of use. Although the residual chlorine was slightly higher in the filtrated water after 2 months of use, the level remaind lower than that in unfiltered water for to after 8 months of use (the end of the useful life of the filter). These findings indicate that this type of water purifier is effective in filtering faucet water, but an appropriate filter-change frequency should be observed according to the water conditions.