We report a feasibility study on liquid-liquid emulsification by static mixers for use in microencapsulation. This study was concerned with developing a quantitative correlation between the size of the microspheres and process parameters. The process parameters considered included operational variables and physical properties associated with both the dispersion and dispersed phases. The effect of mixing element design on mixing efficiency and particle-size distribution was evaluated using three different static mixers. The performance of static mixers and conventional continuously stirred-tank reactors was assessed in several different aspects. Dimensional analysis was used to establish a correlation based on protein-free poly(lactic acid-co-glycolid acid) and poly(methyl methacrylate) microspheres in an oil-in-water emulsion using 1/4 ＇＇, 1/2 ＇＇ and 1 ＇＇ static mixers. This correlation accurately described the preparation of protein-loaded microspheres and provided large-scale microsphere production with a empirical basis.