The density, degree of crystallinity, melting temperature, thickness, frequency and type of unsaturated groups accessible and inaccessible to bromine in chloroform, and the frequency of methyl groups have been determined for five polyethylene (PE) films. Attempts to correlate the diffusion coefficients in the PE or the PE/methanol partition constants for N,N-dimethylaniline (DMA) and one of the microscopic or macroscopic properties of the polymers were unsuccessful. The only roughly physically meaningful relationships found are between the diffusion coefficients and the sum of the frequency of methyl groups and double bonds accessible to bromine in chloroform or the amorphous and interfacial contents of the films, For the PE film of highest crystallinity, two diffusion coefficients were required to obtain a good fit to the data.