The crystallization process and its influence on the microstructures and in turn the ferroelectric and electromechanical properties of poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer were investigated. It was found that, in addition to the crystallites formed at the isothermal crystallization temperature T-x, further crystallites form during the rapid cooling from T-x to room temperature. The proportion of lower melting crystallites increases with T-x, and for T-x = 142 degreesC, this proportion is more than 90%. The experimental results show that the lower melting crystallites have a higher fraction of the all-trans conformation (and thus more polar-phase component) than the crystallites formed at T-x. As a result, the higher T-x samples show an increased polarization hysteresis and reduced electric field induced strain response. For example, the strain is reduced from -5.9 to -4.2% as T-x is increased from 112 to 142 degreesC. In addition, the experimental results in combination with other reported results indicate that CFE units are included in the crystalline lattice. Consequently, the influence of CFE on the ferroelectric behavior of the polymer is through the defects induced in the crystal lattice.