The diffusion coefficients (D) of n-alkanes, n-pentane and n-decane, and 1,4-dioxane as solvent in poly(gamma-benzyl L-glutamate) (PBLG) gel with highly oriented a-helical chains were measured by pulsed field gradient spin echo H-1 NMR spectroscopy, of which the structure was determined by X-ray diffraction. From the experimental results, it was found that the diffusion coefficients of n-pentane and n-decane in the PBLG gel for the direction parallel and perpendicular to the magnetic field are D-parallel to = 8.4 x 10(-6) cm(2)/s and D-perpendicular to = 6.4 x 10(-6) cm(2)/s, respectively, and D-parallel to = 6.1 x 10(-6) cm(2)/s and D-perpendicular to = 5.0 x 10(-6) cm(2)/s, respectively, which correspond to the directions parallel and perpendicular to the a-helical main chain.