The surface free energies of various polyester surfaces have been determined from contact angle measurements using several liquid types. The geometric mean, the harmonic mean, and Fowkes' methods for obtaining the components of surface free energy have been compared for poly(L-lactic acid) (PLLA), poly(DL-lactic acid) (PDLLA), poly(hydroxybutyrate) (PHB), and poly(hydroxybutyrate-hydroxyvalerate) (PHB-HV) copolymers. Polymer films were obtained by solution casting onto a number of smooth substrates, ranging from high-energy surfaces (aluminum, mercury, glass, and freshly cleaved mica) to low-energy surfaces [poly(ethyleneterephthalate) (PET), polytetrafluoroethylene (PTFE), and air]. Results show that the dispersion and polar surface free energy components of polyester surfaces cast against high surface energy (hydrophilic) substrates decrease with aging time toward a stable value. However, when cast against low surface energy substrates, the surface free energy of the resulting polymer/substrate-contacting surface was independent of aging time.