Ultrafiltration　(UF)　of　reservoir　water　for　drinking　proposes　was　performed　in　a　crossflow　filtration　with　frequent　membrane　backwash.　The　effects　of　operating　condition　and　raw　water　quality　on　UF　behavior　were　investigated.　The　membrane　flux　decreases　with　increasing　turbidity　and　there　is　a　somehow　linear　relationship　between　membrane　flux　and　the　log　of　turbidity.　Permeate　flux　increase　with　increasing　the　transmembrane　pressure　(TMP)　and　the　permeate　flux　increase　slightly　when　the　TMP　is　added　to　a　certain　level.　Chemical　analyses　of　the　permeate　water　showed　that　drinking　water　regulations　were　fulfilled.　UF　treatment　provided　effective　turbidity　removal.　UF　membrane　also　perfectly　removes　all　coliform　bacteria.　With　the　exception　of　one　weak　positive　effect　in　raw　water,　the　genetoxic　activities　of　raw　water　and　ultrafiltrated　water　samples　are　negative.