Four kinds of terpenes, i.e. l-menthol, S-(-)-beta-citronellol, [(1S)-endo]-borneol, and R-limonene, were fixed on a cellulose acetate membrane by plasma polymerization method at various periods of plasma irradiation. The fractional fixations of terpenes increased with increasing time of plasma irradiation. The optical resolutions of racemic tryptophan (DL-Trp) solutions were performed by the dialysis and the ultrafiltration using the plasma polymerized membranes, All the membranes were permeable with respect to the D-isomer of tryptophan in preference to the L-isomer. The larger value of separation factor was obtained at lower volume flux. The maximum value of separation factor obtained for DL-Trp was 9.5 at volume flux J(v) = 4.7 x 10(-8) m s(-1). The solute permeabilities and apparent viscous parameters were evaluated from the dialysis and ultrafiltration data, respectively. A linear relation between the solute permeability and the ratio of apparent viscous parameters was obtained. It is indicated that the strength of chemical interaction between the amino acid solute and the terpene fixed in the membrane has a high influence on the solute flow inside the membrane pore.