The separation of a chlorinated hydrocarbon from a dilute aqueous solution through a crosslinked acrylate copolymer-porous substrate composite membrane by pervaporation was investigated. Poly(n-butyl acrylate-co-acrylic acid) and poly(n-butyl acrylate-co-2-hydroxyethyl acrylate) were synthesized and composite membranes were prepared, which were made from the crosslinked polymer and a porous substrate. Pervaporation measurement was carried out for a dilute aqueous solution of 1,1,2-trichloroethane at 25 degrees C and under a vacuum on the permeate side (below 10 mmHg). The separation factor, overall flux, 1,1,2-trichloroethane concentration in the membrane, and the degree of swelling decreased with increase in the acrylic acid or 2-hydroxyethyl acrylate content of the acrylate copolymer. The influence of the crosslinking agent content on the pervaporation performance was small, and the separation factor and the overall flux showed a convex curve. The structure of the crosslinking agent had no effect on the separation. The influence of the pore size of the substrate and the thickness of the polymer layer on the separation of 1,1,2-trichloroethane was observed.