Microchannel (MC) emulsification is a novel technique for preparing monodispersed emulsions. This study investigates the preparation of monodispersed water-in-oil (W/O) emulsions by means of a hydrophobic MC. The effects of surfactants, the properties of continuous oil phases and the flow velocity of the dispersed water phase through the channels on the MC emulsification were studied. The surfactants should be dissolved in the continuous oil phase to create water droplets from the MC without continuous outflow. There was an optimal HLB of surfactant for the monodispersity and stability of the prepared emulsions. Hexaglycerin pentaoleate (PO-500; HLB, 4.9) was found to be suitable for preparing the stable water-in-ethyl oleate emulsion and water-in-tetradecane emulsion. The average diameters and the coefficients of variation of the prepared emulsions were 27.4 mum and 20.6% for the water-in-ethyl oleate emulsion, and 19.1 mum and 4.2% for the water-in-tetradecane emulsion. Hexaglycerin condensed ricinoleic acid ester (HGCR) was suitable for preparing stable water-in-triolein emulsions, The average diameter and coefficient of variation of the emulsion were 39.8 mum and 6.5%. The effects of the viscosity and the hydrophobicity of the continuous oil phase were investigated, Monodispersed emulsions were prepared in the hydrophobic oil phases because hydrophobic oil phases prevent wetting of the MC plate with the water phase. The droplet diameter increased with an increase in viscosity of the continuous oil phase. When the high-viscosity continuous oil phase was used, droplet diameter increased with an increase in the now velocity of the dispersed water phase through the channel.