Alkanethiolates have been widely used as chemisorbates to modify gold surfaces, in spite of their relatively poor oxidative stability. We introduce gold-chemisorbing block copolymers bearing an anchoring block of poly(propylene sulphide) (PPS), selected in the expectation of greater stability. These materials offer a more robust approach to surface modification of gold. As an example, a triblock copolymer with poly(ethylene glycol) (PEG) was selected, with the goal of minimizing biological adsorption and adhesion. The copolymer PEG(17)-bl-PPS25-bl-PEG(g) chemisorbed to form a dense monolayer of 226 +/- 26 ng cm(-2), similar to2.2 nm thick. The copolymeric adlayer was much more stable to oxidation than commonly used alkanethiolates. Its presence greatly reduced protein adsorption (>95%), even after exposure to whole blood serum (>55 mg ml(-1)), as well as cell adhesion over long culture durations (>97%). PPS-containing copolymers are an attractive alternative to alkanethiolates, and PEG-bl-PPS-bl-PEG presents a powerful example for use in biodiagnostic and bioanalytical devices.