In this study we report the direct mechanical measurement of enhancement of surface energy of polyethylene films due to corona treatment. Surface energy was measured using the surface forces apparatus (SFA). Unlike practical adhesion tests, the SFA measurements are free from dissipative effects. The results of direct surface energy measurements using the SFA were compared to the contact angle measurements. The extent of modification was controlled by varying the corona energy density. The surface composition is measured using X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectroscopy (SSIMS). The surface energy of polyethylene increases from 33 to 55 mJ/m(2) due to corona treatment. The surface energy estimated from contact angle measurements varied depending on the probe liquids used and the model used to analyze the data.