The direct production of hydrogen peroxide from H-2 and O-2 has been investigated in two types of microreactors: (1) a single-channel microreactor with a washcoat of catalyst and (2) a multichannel microreactor with eight parallel channels, where the catalyst was grown as a thin film. The multichannel microreactor mimics features of a monolith reactor, where the catalyst is contained in a structured honeycomb. The Taylor (slug) flow in a microchannel reactor under three phase (gas-liquid-solid) conditions enhances the mass transfer over the phase boundaries. The influence of liquid and gas flow rate, pressure drop, solvents, support materials and metal dispersion on the reaction were investigated in order to screen for optimal operation conditions. The productivity in the microchannel reactors increases approximately with the square root of the liquid flow rate, verifying the Taylor-flow model. (c) 2006 Elsevier B.V. All rights reserved.