The invention relates to crosslinkable compositions based on organosilicon compounds and having controllable modulus, to a process for their preparation and to their use, said compositions comprising (a) polymers of the formula X.sub.nR.sub.3-nSi-A-SiR.sub.2--(CH.sub.2).sub.3NHY (I) (b) polymers of the structure X.sup.1.sub.kR.sup.5.sub.3-kSi-A.sup.1-SiX.sup.1.sub.kR.sup.5.sub.3-k (II) (c) optionally, silanes of the formula R.sup.6.sub.mSiX.sup.2.sub.4-m (III) and/or partial hydrolyzates thereof, and (d) optionally, silanes of the formula R.sup.4.sub.oSiR.sup.7.sub.pX.sup.3.sub.4-o-p (IV) and/or partial hydrolyzates thereof, where X, X.sup.1 and X.sup.3 are OH or a hydrolyzable group, R, R.sup.4, R.sup.5, and R.sup.7 are hydrocarbyl groups, and A is a divalent linking group.