Smooth and spherical alginate microspheres and nylon-membrane bound microcapsules were formed in an air-agitated, liquid-liquid mixer by emulsification/ internal gelation and interfacial polymerization respectively. The mean diameter of the alginate microspheres ranged from 100 to 800 mu m, and was controlled by process modifications. Increase in emulsifier concentration, gas flowrate, and emulsification time resulted in smaller microsphere size as did a decrease in liquid height. Increase in the dispersed phase viscosity resulted in a longer emulsification time required for approaching a minimum microsphere size. Microspheres could be formed with the proportion of dispersed phase approaching 30%. The yield of alginate microspheres was 70%, with loses attributed to incomplete recovery during washing and filtration operations. The yield of DNA encapsulation within the fraction of recovered microspheres, was 94%. The small loss was thought to occur by surface release during the washing of the microspheres.