A H-1 NMR method is described for examining crystallinity, chain mobility, and crystallite size in real time during polymer crystallization. The method is demonstrated by following the crystallization of natural rubber at - 10 degreesC. At selected stages during the crystallization, a Bloch decay was recorded along with Goldman-Shen decays for a series of mixing times using a filter duration to destroy the rigid-phase magnetization. The fast-relaxing components of the Bloch and Goldman-Shen decays correspond to the rigid/crystalline fraction of the sample and were fitted to Gaussian functions. The slow-relaxing components were obtained experimentally using the Goldman-Shen sequence measured with a short mixing time (1 ms). By combining the fitted Gaussian portions with the experimentally determined slow-relaxing components, the Bloch and Goldman-Shen decays could be analyzed across the entire crystallization process. The Bloch decays provided information on the amount and nature of the rigid fraction, while the Goldman-Shen spin-diffusion data provided information on domain size. The formation of noncrystalline rigid domains was observed for the initial stages of the crystallization process. Data clearly indicate lateral growth of crystallites with relatively uniform thickness during the primary crystallization process. Later stages of crystallization are characterized by increasing heterogeneity in crystalline density and perfection.