Emulsification is usually performed using high-pressure homogenizers and rotor/stator systems. In the dispersing zone of these machines high shear stresses are applied to deform and disrupt large droplets of a premix. Membrane emulsification is a new emulsification technology based on the use of a microporous membrane. In this process, the disperse phase is pressed through the pores into the continuous phase where the droplets are formed. The droplets reaching a critical diameter detach from the membrane surface under the influence of shear forces caused by the flow of the continuous phase. In this investigation, polypropylene hollow fibers with 0.4 mum pores and 1.7 mm inside diameter were used to produce water-in-oil (W/O) emulsions consisting of demineralized water as the dispersed phase, mineral oil Velocite no. 3 as the continuous phase, and polyglycerol polyricinoleate (PGPR 90) as the emulsifier. The size of water droplets in the prepared emulsions and the droplet size distribution strongly depended on the membrane pretreatment procedure, the transmembrane pressure, the dispersed phase content and the emulsifier concentration. The emulsion droplets with a mean Sauter diameter of about 0.3 mum and a span value between 1.1 and 1.6 were produced using 10 wt.% emulsifier at a transmembrane pressure below 50 kPa. Droplet sizes smaller than pore size were obtained; this effect is explained by existing of an oil film inside the pores reducing the effective pore size. This effect could provide a new possibility for producing small droplets of uniform distribution.