The deformation and fracture behavior is characterized for poly(vinylidene fluoride-trifluorethylene) 75/25 mol% copolymer films under uniaxial tension. The films are prepared by solution casting and then annealed at 135 degrees C for 2 h, 6 h, and at 140 degrees C for 2 h, respectively. The results demonstrate that all the copolymer films show the typical polymeric brittle fracture behavior. The copolymer film annealed at 135 degrees C for 2 h shows the best combination of ductility and strength, with the fracture strain reaching 9.6%. Scanning electron microscope observation and X-ray diffraction analysis are carried out to examine the morphology and microstructure change during uniaxial tension. It is revealed that the average size of the polymer crystallites increases while the content of the crystallites hardly changes as the annealing time or temperature increases. Reduction in the crystallite size leads to enhanced fracture strain and strength for the copolymer film under uniaxial tension. POLYM. ENG. SCI., 48:2335-2339, 2008. (C) 2008 Society of Plastics Engineers