Surface free energy (SFE) is a property resulted from the chemical structure and the orientation of the molecules at the surface boundary of the materials. For solids, it can be calculated from the contact angles of liquid drops with known surface tension, formed on the solid surface. There are various SFE evaluation methods based on different theoretical assumptions. In this study, SFE and the dispersive, polar, acidic and basic components of the SFE of a polymeric material, poly(methyl methacrylate) (PMMA), were calculated by using Zisman, Saito, Fowkes, Berthelot, Geometric mean, Harmonic mean, and Acid-base approaches. The results obtained from various liquid couples or triplets were compared. (C) 2007 Wiley Periodicals, Inc.