Biocomposites were made with nonwoven hemp mats and unsaturated polyester resin (UPE). The hemp fiber volume fraction was optimized by mechanical testing. The effect of four surface treatments of industrial hemp fibers on mechanical and thermal properties of biocomposites was studied. The treatments done were alkali treatment, silane treatment, UPE (matrix) treatment, and acrylonitrile treatment. Bending strength, modulus of elasticity, tensile strength, tensile modulus, impact strength, storage modulus, loss modulus, and tan 5 were evaluated and compared for all composites. The mechanical as well as thermal properties of the biocomposites improved after surface treatments. The properties of the above biocomposites were also compared with E-glass-mat composite. To achieve balance in properties, a hybrid composite of industrial hemp and glass fibers was made. (c) 2005 Wiley Periodicals, Inc.