The pervaporation tests for n-hexane, 2-methylpentane (2-MP), and 2,3-dimethylbutane (2,3-DMB) were performed using an MFI-type zeolitic membrane at 303 K. In the unary systems, those fluxes followed the order n-hexane >> monobranched hexane (2-MP), > dibranched hexane (2,3-DMB). The ideal selectivities of n-hexane/2-MP and n-hexane/2,3-DMB were 37 and 50, respectively. n-Hexane preferentially permeated in the measurements of a binary mixture of n-hexane/2-MP and n-hexane/2,3-DMB. The feed composition dependence in separating n-hexane/ 2,3-DMB binary mixtures was studied. The separation factor for the 50/50 n-hexane/2,3-DMB mixture exceeded 120, which was much greater than 54 in the 50/50 n-hexane/2-MP system. When the feed concentration of n-hexane was 10 mol %, the separation factor alpha(n-hexane/2,3-DMB) at the steady state was as high as 270. n-Hexane effectively inhibited the permeation of 2,3-DMB, even when the concentration of n-hexane was very small.