This paper describes a study conducted at the University of New Hampshire on three polysulfone hollow fiber ultrafiltration membranes. The results show that the membranes can provide a consistent means of removing Giardia, Cryptosporidium, and viruses to a level greater than or equal to that required by the Surface Water Treatment Rule (SWTR). Specifically, the microbiological challenges performed on the PM10, PMPW, and PM500 membranes demonstrated that: the PMPW was capable of producing water with no Giardia cysts and Cryptosporidium oocysts in the permeate; and the PMPW membrane removed 4 logs and greater of MS2 bacteriophage when sufficient quantities were present in the influent.