The interaction of a diffusant with the polymer matrix may cause difficulties in the determination of its self-diffusion coefficient by the pulsed-field-gradient NMR technique. We report here the study of the interaction of ethylene glycol with poly(vinyl alcohol) (PVA) in aqueous solutions and gels by NMR spectroscopy and the elucidation of the diffusion coefficients of the free and bound ethylene glycol molecules which coexist in the PVA-water system. The fraction of bound ethylene glycol increases as a function of PVA concentration, and a binding constant of ca. 1.7 x 10(3) M-1 was estimated. Various H-1 NMR parameters such as chemical shifts, self-diffusion coefficients, and spin-lattice and spin-spin relaxation times have been determined to study the interactions. The free and bound ethylene glycol molecules have different chemical shifts, NMR relaxation times, and self-diffusion coefficients at various polymer concentrations.