Contact angles of water and methylene iodide were measured as a function of UV/O-3 treatment time for three polymers : poly(methyl methacrylate) (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE). Surface roughnesses were also measured. Surface free energies were then calculated using relationships developed by Kaelble and Neumann. The surface energy of polycarbonate was found to increase (similar to 60%) during UV/O-3 treatment. However, calculations on PMMA were hampered by the formation of a water soluble surface product. On PTFE surfaces, the UV/O-3 treatment etched the surface, causing large increases in surface roughness, rendering contact angle measurements impossible. It is concluded that care must be taken in interpreting contact angle measurements and surface energy calculations on UV/O-3 treated polymer surfaces.