Real-time in situ observations of isolated spherulitic growth in poly(ethylene oxide) (PEO, M(n) = 100 000) and alpha-phase isotactic polypropylene (iPP, M(eta) = 250 000) have been carried out by using video microscopy coupled with a computer image-processing system. A macroscopic latent heat transfer model, which is consistent with the linear growth velocity measured experimentally during spherulitic growth, has been developed and tested in conjunction with Hoffman’s nucleation theory. It was found that the latent heat release during spherulitic solidification is compatible with the linear growth velocity.