Proton nuclear magnetic resonance imaging (NMRI) was used to study the different physical and spatial microstructures present in an unfilled accelerated-sulfur cured high-vinyl polybutadiene material. Samples of different formulations were cured at 150-degrees-C from 20 to 120 min in order to monitor the changes associated with the cure times. Voids and other inhomogeneities were detected on the basis of magnetic susceptibility differences. A solvent imaging method using cyclohexane was used to probe the different morphological defects. Reversion, a process involving a decrease in the overall cross-link density, was observed in the samples cured for 120 min. Sample morphological features as small as 0.07 mm can be detected.