We investigate the effects of high shear rate and a melt-insensitive, organophosphate nucleating agent on shear-induced crystallization of four isotactic polypropylenes using a sliding plate rheometer under isothermal, low-supercooling conditions. We used a bifurcated optical fiber probe to measure light intensity and a shear stress transducer to monitor the simultaneous viscoelastic response to small-amplitude oscillatory shear. The two techniques complement each other; at early times of crystallization, large attenuation in the light intensity is observed, whereas during the later stages, a major change in the viscoelastic response occurs due to the growing volume fraction of spherulites. In contrast to quiescent crystallization, the nucleation pathway of nucleated polymers after a brief, strong shear is little influenced by the nucleating agent but strongly affected by molecular weight. The early kinetics of non-nucleated polymers is more strongly enhanced by shear than that of nucleated polymers. Increasing either shear rate or strain accelerates crystallization, and we found the product of shear rate and strain to be useful for correlating our data. POLYM. ENG. SCI., 52:835-848, 2011. (C) 2011 Society of Plastics Engineers