This study presents quantitative results related to in situ investigation of the microstructural evolutions of high-density polyethylene with deformation. These results were obtained thanks to a novel technique (IPSLT) based on the polarized light scattering transport phenomenon. The heterogeneities produced during whitening of the polymer bulk are characterized at the mesoscale level (from hundred of nanometers to a few micrometers). The technique is described as well as the identified parameters it provides, namely: the average size of the scatterers, the anisotropy developed in the medium, and the light transport length, representative of both the volume fraction and size of the heterogeneities. Results obtained during video-controlled tensile experiments confirm those obtained previously with X-ray microtomography. They put forward the role of morphological transformations of the amorphous/crystalline phases (especially regarding the creation of fibrillar assemblies) rather than the cavitation phenomenon. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012