Studies on the crystallization of polymers are usually carried out by dilatometry, differential scanning calorimetry (d.s.c.) and optical microscopy. These methods have been widely used in the analysis of crystallization kinetics using the Avrami equation. Direct determination of nucleation rate and density is only possible by the optical microscope technique. We have employed a new technique for studying the crystallization behaviour of polymers by using a dynamic mechanical method. This method is capable of detecting the onset of nucleation. Semiquantitative data on the nucleation density and the initial crystallization rate may also be deduced by this method. Results from the dynamic mechanical method are cross-compared with d.s.c. and optical microscope data for polypropylene, polyethylene and their blends, and are shown to be mutually consistent.