(Chemical Equation Presented) The probable reaction pathways for propylene epoxidation with O2 and H2 in the presence of trimethylamine on trimethylsilylated Au-Ba(NO3)2/ titanosilicate catalyst are discussed (see figure). The use of trimethylamine as a gas-phase promoter for nanoparticulate gold catalysts leads to a direct one-stage production of propylene oxide (PO) with steady space-time yields comparable to values for current industrial ethylene oxide production. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.