The effective diffusivities of glucose and its linear analog glucitol were measured by a liquid chromatographic technique at 30 degrees C within water-filled silica and aluminosilicate catalysts of mean pore size ranging from 7.4 to 116 Angstrom. For glucose, the effective diffusivity decreased from 1.08 x 10(-6) to 1.77 x 10(-9) cm(2)/s as the mean pore size decreased from 116 to 7.4 Angstrom. All values were significantly lower than the molecular diffusivity of 7.02 x 10(-6) cm(2)/s. The effective diffusivities for glucitol were three times lower than those for glucose over the same pore size range due to differences in solute size, structure, and solute-adsorbent interactions. The 8.6 Angstrom glucose molecule-was able to diffuse into the 7.4 Angstrom Y-zeolite pore, possibly as its acyclic form. However, the 9.7 Angstrom glucitol molecule could not diffuse into the Y-zeolite pore. The reduced diffusivity was correlated to the reduced pore diameter using the Ternan model.