The artificial AN69 membrane (Hospal), a synthetic copolymer composed of acrylonitrile and sodium methallyl sulphonate suitable for pancreatic islet encapsulation, was submitted to physicochemical treatment (Corona discharge) to improve its insulin permeability. X-ray photoelectron spectroscopy (XPS) analysis of the AN69 membrane indicated the presence of up to two molecular layers of glycerol at its surface while the surface energies revealed the presence of hydrophilic sites (-SO3Na/glycerol) located at the membrane surface and acrylonitrile hydrophobic groups inside the material. The Corona discharges decreased the number of glycerol molecules at the membrane surface and from a biological point of view, produced a threefold increase in insulin diffusion. Furthermore, the biocompatibility of the treated membrane was preserved after 1 year of intraperitoneal implantation. The increase in insulin permeability should result from a decrease of the membrane polarity and of a steric hindrance in pores. Thus, Corona discharge treatment may serve to optimize the properties of artificial membranes used for pancreatic islets encapsulation.