Organopolysiloxane compositions are provided which are curable by condensation reaction taking place between a first component, hydroxy-terminated diorganopolysiloxane and a second component, organohydrogenpolysiloxane by aid of a third component, a condensation catalyst, and which are made to have their pot life extended by adding a fourth component, acyloxysilane, optionally in combination with a carboxylic acid, as a condensation retarder. The addition of the retarder does not adversely effect the curing velocity of the composition even at an elevated temperature and the properties of the cured composition.