Abstract: A novel crosslinkable composition comprising(A) an organosilicon compound having radicals containing aliphatic carbon-carbon multiple bonds,(B) an organosilicon compound having Si-bonded hydrogen atoms,(C) a catalyst which promotes the addition of Si-bonded hydrogen onto aliphatic multiple bonds and, optionally,(D) agents which retard the addition of Si-bonded hydrogen onto aliphatic multiple bonds at room temperature,wherein the organosilicon compounds having Si-bonded hydrogen atoms (B) used are ones comprising(a) on average per molecule, at least one structural unit of the formula--Z--SiR.sub.x (OSiR.sub.3-a H.sub.a).sub.3-x (I),whereR is an identical or different monovalent, optionally halogenated hydrocarbon radical which is free of aliphatic multiple bonds and has from 1 to 8 carbon atoms per radical,Z is a divalent aliphatic hydrocarbon radical having from 2 to 12 carbon atoms per radical,a is 1, 2 or 3, andx is 0 or 1.