A primer composition comprises (a) a fluoroalkylene or fluoropolyether compound having at least one alkenyl radical and at least one hydrolyzable silyl radical, (b) an organic titanic acid ester, (c) an organic tin compound, and (d) a silane compound. The primer composition is fully adherent to various substrates of metals, glass, ceramics, cement, mortar, carbon, and plastics, and is particularly suited for use with a thermosetting elastomer composition based on a polymer having at least two alkenyl radicals and a perfluoropolyether structure in its backbone.