Organopolysiloxane compositions are provided which are curable to elastomers and exhibit an excellent adhesion to the various surfaces of metals, glasses, ceramics and the like. The organopolysiloxane composition comprises (a) a diorganopolysiloxane terminated at both chain ends with vinyl groups directly bonded to the terminal silicon atoms in a molecule, (b) an organohydrogenpolysiloxane having at least two hydrogen atoms bonded directly to the silicon atoms in a molecule and at least one epoxy or ester group bonded to the silicon atom through an Si--C linkage in a molecule, and (c) a platinum catalyst. The compositions are useful for applications, such as, potting of electronic circuit units, coating of electrical parts, impregnation of fly-back transformers for television sets and coating of junctions for semiconductor devices.