Triethoxysilyl-modified polychloroprene (CR) latex was synthesized by the emulsion copolymerization of 2-(3-triethoxysflylpropyl)-1,3-butadiene with chloroprene. This latex was mixed with unmodified CR latex and tetraethoxysilane to obtain CR-silica composites by sot-gel reaction in the latex. SEM observation showed that the silica particles in un-vulcanized composites have various diameters ranging from 0.1 to 0.6 mu m, and their size became larger with the decrease of the silica content. Vulcanized CR-silica composites showed that the tensile modulus and tear strength improved with an increase of the amount of modified CR. (c) 2005 Wiley Periodicals, Inc.