I.r. and high-resolution solid-state C-13 n.m.r. spectra, as well as proton relaxation times T-1(H) and T-1 rho(H) of poly(ethylene oxide) (PEO)/atactic poly(methyl methacrylate) (a-PMMA) blends in the solid state, with PEO weight fractions of 10, 30, 50 and 70% were measured. Infra-red spectra of pure PEO with various molecular weights were also measured. The measurements indicate that no large changes in the content of the ttt conformational structure of PEO with blending occur. In the blends containing 30% PEO or less, only a negligible amount of crystalline PEO has been found. From the T-1(H) and T-1 rho(H) relaxation times it follows that all the blends studied are completely homogeneous on the scale of 20-70 nm; at the same time at least part of the PMMA and PEO chains are intimately mixed in the amorphous phase with the average size of the PMMA domains being below 6 nm, T-1(H) values and C-13 n.m.r. linewidths indicate changes in the mobility of polymer segments with blending.