We have measured the self-diffusion coefficients of a series of solute probes, including ethylene glycol and its oligomers and polymers in aqueous solutions and gels of poly(vinyl alcohol) (PVA) using the pulsed-gradient spin-echo NMR techniques. In an effort to link the diffusion properties of small and large molecules in polymer systems, we have selected this group of diffusant probes with various molecular weights, ranging from 62 to 4000. The self diffusion coefficients of the solute probes decrease with increasing PVA concentrations (from 0 to 0.38 g/mL) and with increasing molecular size of the probes. The temperature dependence of the self-diffusion coefficients has also been studied for ethylene glycol and poly(ethylene glycol)s of molecular weights 600 and 2000. Energy barriers of 30.0, 36.5, and 39.0 kJ/mol have been calculated respectively for the probes, in the temperature range 23-53 degrees C. The experimental data are used to fit a new physical model of diffusion (Petit et al. Macromolecules, 1996, 29, 6031), which is shown to be successful in describing the effects of polymer concentration, temperature, and molecular size of the diffusants on the self-diffusion coefficients of small and large molecular probes in the polymer system.