The invention describes crosslinkable compositions comprising(1) organosilicon compounds which contain radicals having aliphatic carbon-carbon multiple bonds,(2) organosilicon compounds having Si-bonded hydrogen atoms or, in place of or in addition to (1) and (2); said composition further comprising(3) organosilicon compounds which contain radicals having aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms,(4) catalysts which promote the addition of Si-bonded hydrogen to aliphatic multiple bonds, and ##STR1## where R.sup.1 and R.sup.2 are as defined in claim 1, and X is a radical of the formula --OH, --Cl, --Br and --CN, with the radical --OH being particularly preferred.