2 H-NMR spectroscopy is applied to measure strain-induced orientational anisotropy of polymer segments in three environments in poly(dimethylsiloxane) (PDMS) elastomers: elastic chains, pendant chains, and PDMS(d) chains dissolved in the network. The elastomers were prepared with systematically-varied structures and selective deuterium labeling. Network features were inferred from macroscopic measurements using statistical and thermodynamic models. The segment order parameter, S, was found to be proportional to λ 2 -λ -1 , where λ is the compression ratio, for the three environments in uniaxially-compressed PDMS networks: elastic chains, pendant chains, and dissolved probe chains. Furthermore, all three environments show the same dependence of the ratio S/(λ 2 -λ -1 ) on the elastic modulus, in the range 0.089-0.29 MPa. These results agree with the recent theoretical predictions of Brereton and Ries (Macromolecules 1996, 29, 2644) and thus support the premise that the excluded volume (entropic) interactions between segments subjected to deformation cause anisotropic averaging of the quadrupolar interaction and thus cause a 2 H-NMR line splitting.