Simultaneous Fourier-transform IR spectroscopic and stress-strain measurements were used to study the II(a)-I(b) crystal phase transformation in poly(vinylidene fluoride) [24937-79-9] under tensile stress at variable temp. From the exptl. data it was shown that, in the investigated temp. interval from 348 to 423 K, the drawing process is inhomogeneous and occurs via formation of a neck. The II(a)-I(b) phase transformation is restricted to temps. below 423 K, and its onset is generally related to the formation of the neck.