Results are reported of an experimental investigation of penetration rate and penetrant concentration profile, in the PMMA-methyl alcohol (MA) system. Penetration of liquid MA, at 22, 30, and 40 degreesC, along annealed or quenched films sandwiched between glass plates, was followed microscopically, and the corresponding concentration profile was studied by two-beam microinterferometry. This experimental approach was shown to provide information not directly obtainable by sectioning followed by colored tracer microdensitometry or by laser interferometry, previously applied to the study of MA across the PMMA film. On the basis of this new experimental evidence, in conjunction with the results of the theoretical investigation reported in part 1, it proved possible to elucidate certain important, but previously obscure, aspects of case II diffusion behavior in this system.