This paper describes the use of hydrophilic grafted and segmented copolyimides to modify the surfaces of polyimide membranes used for microfiltration processes the synthesis and characterisation of the copolymers are described in an accompanying paper. The copolymers have either hydrophilic grafts or hydrophilic main-chain segments based on poly(ethylene oxide). Samples for fouling studies were prepared by incorporating a proportion of copolymer while forming a membrane from a hydrophobic polyimide. Both grafted and segmented copolyimides reduced fouling as assessed by measurements of protein (radio-labelled bovine serum albumin) absorption. Fouling propensities were investigated for different copolymer contents and compositions. Variations in composition included changes in the aromatic dianhydrides and aromatic diamines used in conjunction with the hydrophilic units.