Anhydride-functional organo(poly)siloxanes having average units of the general formula ##EQU1## in which the R(s) are the same or different and represent a monovalent hydrocarbon radical or a monovalent halogenated hydrocarbon radical having from 1 to 18 carbon atom(s) per radical, A represents a radical of the formula ##STR1## in which R.sup.1 represents a hydrogen atom or a monovalent hydrocarbon radical or a monovalent halogenated hydrocarbon radical having from 1 to 12 carbon atom(s) per radical and R.sup.2 represents a hydrogen atom or a monovalent hydrocarbon radical having from 1 to 12 carbon atom(s) per radical, or the two radicals R and R.sup.2 together represent a divalent hyrocarbon radical having from 3 to 5 carbon atoms per radical, R.sup.3 represents a hydrogen atom or a monovalent hydrocarbon radical having from 1 to 4 carbon atom(s) per radical, with the proviso that R.sup.3 is a hydrogen atom if the two radicals R.sup.1 and R.sup.2 together represent a divalent hydrocarbon radical having from 3 to 5 carbon atoms per radical, R.sup.4, which may be the same or different, represent a hydrogen atom, a halogen atom or a cyano radical, a is 0 or 1, with an average of from 0.003 to 1.0, b is 0, 1, 2 or 3, with an average of from 0.05 to 2.5, and the sum of a+b is an average which is not greater than 3, with the proviso that at least one A radical is present per molecule.