The present invention provides a process for using nanosized copper, nanosized copper oxides, nanosized copper chlorides, other nanosized copper salts, and mixtures thereof, as sources of catalytic copper in the Direct Synthesis of trialkoxysilanes of the formula HSi(OR).sub.3 wherein R is an alkyl group containing from 1 to 6 carbon atoms inclusive. The nanosized copper, nanosized copper oxides, nanosized copper chlorides, other nanosized copper salts, and their mixtures of this invention have average particle sizes that are in the range from about 0.1 to about 600 nanometers, preferably from about 0.1 to about 500 nanometers, and most preferably from about 0.1 to about 100 nanometers. Nanosized sources of catalytic copper afford high dispersion of catalytic sites on silicon and contribute to high reaction rates, high selectivity and high silicon conversion. The nanosized copper catalyst precursors of the invention permit the use of substantially reduced levels of copper compared to conventional practice.