Polyurethane catheters were irradiated with electron-beam. We looked at the way the catheter is physically and chemically modified after incubation in differ ferent media. An extracting medium (methanol) was compared to other oxidative, enzymatic, and saline aqueous media, mimicking some aspects of biological fluids. Irradiation had a strong impact on the stability of polymer during incubation. For nonirradiated samples incubated in aqueous media, only a small diffusion of additives was observed; no oligomer release was put into evidence, and the polymer was almost not degraded. Put the chain branching that occurred because of irradiation created some weaknesses in the polymer chains: irradiated samples were mostly sensitive to chain scission and oligomers released during incubation; this trend increased with the irradiation dose. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 3113-3120, 2009