Abstract: This invention relates to a process for preparing alkoxysilanes of the general formula (R.sup.2) .sub.a SiH(OR.sup.1).sub.b in which R.sup.1 is a lower alkyl group with 1 to 6 carbon atoms, R.sup.2 is an aliphatic or aromatic hydrocarbon radical with 1 to 8 carbon atoms, a is 0 or 1, and b is 2 or 3 by the reaction of metallic silicon, an alcohol, and an acetal and/or an orthocarboxylic acid ester in the presence of a copper catalyst and provides a novel process for preparing directly and advantageously alkoxysilanes having one hydrogen atom linked to the silicon atom, particularly alkyldialkoxysilanes and trialkoxysilanes.