Measurements of piezoelectric and pyroelectric activity, density, and x‐ray pole figures were used to study the effect of thermal aging on the state of polarization in polyvinylidene fluoride. A rolled and poled  &bgr;‐phase specimen of polyvinylidene fluoride was subjected to thermal aging which consisted of temperature cycling between room temperature and successively higher maximum temperatures,TMAX, whereTMAXranged from room temperature to 164 °C. We found that the room temperature piezo and pyroelectric activity decreased linearly as a function ofTMAXfrom 75 °C to 164 °C at which temperature the specimen had 30% of its original activity; a linear extrapolation of these data to zero activity yielded a temperatureTc=207 °C. From density measurements at room temperature, crystallinity was calculated and found to remain constant during thermal cycling. X‐ray pole‐figure observations of the (200) (110) composite diffraction of the  &bgr;‐phase crystal showed single‐crystal texture of the rolled specimen and confirmed the six‐site model of dipole orientation. Changes in x‐ray intensity at the six sites on the pole figure, as a function of thermal aging, were associated with the depolarization process which occurs via a 60° rotation of dipoles away from the direction of primary polarization. Based on these data, we propose a model which describes the state of polarization in polyvinylidene fluoride and from which we calculate the fraction of dipoles in the crystalline state contributing to the polarization.