In this work, the effect of medium pressure plasma treatment on thin poly-e-caprolactone (PCL) layers on glass plates is investigated. PCL is a biocompatible and biodegradable polymer which potentially can be used for bone repair, tissue engineering and other biomedical applications. However, cell adhesion and proliferation are inadequate due to its low surface energy and a surface modification is required in most applications. To enhance the surface properties of thin PCL layers spin coated on glass plates, a dielectric barrier discharge (DBD) at medium pressure operating in different atmospheres (dry air, argon, helium) was used. After plasma treatment, water contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to examine the PCL samples. These measurements show that the medium pressure plasma treatment is able to increase the hydrophilic character of the samples, due to an incorporation of oxygen groups at the surface and that the surface roughness is significantly decreased after plasma treatment. (C) Koninklijke Brill NV, Leiden, 2011