Elastomeric networks prepared from atactic polypropylene were crosslinked with γ-irradiation. The stress-optical behavior of the unswollen networks was studied over a variety of elongation ratios and temperatures. At constant length, the stress f/A increases markedly at the glass transition temperature Tg, but the value of Tg does not change discernibly with increasing elongation. The unswollen networks exhibit negative birefringence for values of the elongation ratio λ below 1,8; however, for values of λ > 1,8, the birefringence becomes positive. This behavior was attributed to the presence of crystallites in the unswollen networks. Polypropylene networks, swollen with 1,3,5-triethylbenzene and tetradecane, were also studied with regard to their stress-temperature and birefringence-temperature relationships. Whereas both the birefringence and stress of elongated networks swollen with the former solvent show a linear dependence on temperature, the birefringence of elongated networks swollen with tetradecane exhibits an anomalous increase at low temperatures which was attributed to poorly developed crystallinity. Values of the birefringence and stress corresponding to swollen networks were used to calculate the values of the optical configuration parameter Δa and its temperature coefficient. Theoretical calculations carried out with the rotational isomeric state model were used to evaluate Δa as a function of the stereoregularity of the chains. It was found that Δa decreases as the proportion of meso diads Pm increases, remaining almost constant for values of Pm > 0,7. The theoretical results of Δa and d In Δa/dT obtained for Pm > 0,4 reproduce very satisfactorily the experimental results obtained on the networks swollen with 1,3,5-triethylbenzene.