In the work described in this paper the dielectric properties of solid solutions of p-nitroaniline in poly(methyl methacrylate), poly(ethyl methacrylate) and poly(n-butyl methacrylate) were measured in the frequency range from 20 to 10(6) Hz and the results obtained were compared with those of the pure polymers. It is shown that the presence of the solute has a strong influence on the relaxation process of poly(methyl methacrylate), and this is ascribed to the formation of hydrogen bonds between the amino group of the solute and the side groups of the polymer. In poly(ethyl methacrylate) this effect is less pronounced and it is absent in the case of poly(n-butyl methacrylate), suggesting that the increasing size of the n-alkyl group prevents hydrogen bond formation between the solute and the polymer.