In this work, we report evidences of cocrystallization in ternary blends made of crystalline ferroelectric poly (vinylidene fluoride-trifluorethylene) [P(VDF-TrFE)] copolymers. Complete cocrystallization has been unequivocally demonstrated by the observation of just one Curie and one Melting temperature in their calorimetric thermograms. These temperatures were intermediary among the respective temperatures of the individual constituents, that is, P(VDF-TrFE)(72/28), P(VDF-TrFE) (63/37), and P(VDF-TrFE)(50/50). Dielectric and X ray diffraction data were used to complement the investigation. The binary blends made of 63/37 and 72/28 copolymers were found to be miscible in the entire range of composition, with the behavior of their Curie temperatures being well fitted by an equation very similar to that proposed by wGordon-Taylor to describe the behavior of the glass transition temperatures in true binary blends. In the ternary crystalline system, we have found evidences that the complete miscibility of the binary blend made of 63/37 and 72/28 copolymers actually drives the P(VDF-TrFE)(50/50) copolymer to accommodate their chains in its binary crystalline structure. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 621-626, 2010