Fillers were synthesized in a 42% acrylonitrile NBR copolymer by using tetraethoxysilane, N-2-aminoethyl-3-amino-, 3-mercapto-, and 3-methacryloxypropyltrimethoxysilane as precursors. The crosslinking systems included., dicumyl peroxide, anhyd. ZnCl2 and SnCl2, ZnO, diphenylguanidine, tetramethylthiuram and dibenzothiazolyl disulfides, S-8, and stearic acid. Dispersion degree of filler was estd. by SEM photomicrography, Crosslinking density (Flory-Rehner eqn.) was detd. via equilibrium swelling in toluene and in toluenic 10% ethylenediamine. The crosslinking system affected formation of the silica fillers and thus also the elastomer properties. The vulcanizates prepared with the aid of 3-methactyloxypropyltrimethoxysilane with ZnCl2 and SnCl2 as crosslinkers, showed higher tensile strengths. The fill were more effective as strengtheners in the sulfur rather than in the peroxide vulcanizates.