The influence of the process parameters on the particle size and microencapsulation efficiency of gelatin microspheres prepared by the emulsification solvent extraction technique was investigated. The processing parameters studied were time and speed of emulsification, gelatin concentration and the presence of a surfactant and its concentration. Increasing duration of emulsification >5 min, and surfactant concentration less than or equal to 1% (w/w) significantly reduced the particle size of the microspheres. Emulsification speed did not influence the particle size significantly. A large increase in particle size was obtained with gelatin concentrations >20% (w/v). Using riboflavin as a model drug, gelatin products differing in Bloom value were tested for a possible dependence of degree of microencapsulation and particle size on the viscosity of the gelatin used. Both degree of microencapsulation (84.2-96.0%) and mean particle size (22.1-32.0 mu m) were found to be independent of the viscosity grade used.