Oil-in-water and water-in-oil nanoemulsions are interesting carriers for respectively oil soluble and water soluble actives. In this study, oil-in-water (O/W) and water-in-oil (W/O) nanoemulsions were prepared by premix membrane emulsification. A coarse emulsion (premix) was injected thanks to a high pressure pump through a Shirasu Porous Glass (SPG) membrane with pore size of 0.5 mu m in order to reduce and homogenize the droplet size. The effect of viscosities on the pressure and droplet size was investigated: the water phase viscosity by increasing glycerol concentration, the oil phase viscosity with mineral oils of different viscosities and the overall emulsion viscosity by increasing the dispersed phase content of the emulsion. The pressure required to break up the droplets inside the membrane pores Delta P-dis did not depend on viscosities, while the pressures generated by the flows through the pipe Delta P-pipe and the membrane Delta P-flow. were proportional to the viscosity of the overall emulsion. W/O nanoemulsions were more difficult to produce and to characterize but thanks to the original set-up working at pressures up to 65 bar and high flowrates, W/O mineral oil nanoemulsions were produced with mean droplets size around 600 nm and flow rate of 50 mL/min. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.