Swirl flow membrane emulsification is a very high disperse phase flux method for high throughput production of emulsions. The extremely vigorous, turbulent flow eddies generated exert an extremely high radial drag force on the membrane wall, which prevents the transition of droplet formation from the dripping regime to the continuous out flow regime, at extremely high disperse flux emulsion production. In the present study, the effects of surfactant, disperse phase flux, viscosity, and swirl flow velocity on the mean droplet diameter (D-50) and droplet size distribution coefficient ( span) of an oil-in-water (O/W) emulsion are analyzed. The results indicated that highly monodispersed emulsions could be prepared at very high dispersed phase fluxes of 2.0 to 15.6 m(3) m(-2)h(-1). The most monodispersed emulsions produced were of D-50 of 33.4 mu m and of span of 0.24, obtained at various process conditions. The emulsion D-50 and corresponding span decreased with swirl flow velocity until the critical velocity of 8.5 m/s, beyond which the D-50 decreased further while its corresponding span increased slightly. The increase of the dispersed phase viscosity resulted in anincrease of the emulsion D-50, while the increase in viscosity ratio in respect to the continuous phase viscosity led to a decrease in D-50. The disperse flux had no significant effect on D-50 until the critical disperse flux of 11.7 m(3) m(-2)h(-1), beyond which the inertial force became the dominant force of droplet formation and the D-50 increased drastically; although it could be counterbalanced at high surfactant concentration and at higher swirl flow velocities.