The isothermal and nonisothermal crystallization kinetics of cis-1,4-polybutadiene has been investigated with respect to the content of cis units and the linearity of the main chain. The rate of spherulite growth increases with chain regularity as the presence of branches as well as segments with different configurations slows the crystallization rate. The major parameter that determines the crystallization rate is the presence in the formulation of heterogeneities that favor the formation of primary nuclei and determine an anticipated onset of crystallization. As the activity of the heterogeneous nuclei depends more on the type and number of foreign particle than on any chain parameter, no straightforward information on the influence of the chain structure on the crystallization rate can be derived by mere calorimetric analysis, at least for analyzed samples. It is only with combined analysis by optical microscopy that comprehensive information on the crystallization kinetics of cis-1,4-polybutadiene can be derived. The results reported in this contribution point out the importance, in polymer science, of preferring complementary instrumentation and not limiting experimental investigations to a single technique of analysis. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1408-1413, 2010