An improvement of the productivity of the preparation process for ultrafine ZnS and CdS particles using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micellar systems is studied. Sufficient quantities of reactants are provided to the reverse micelles by using H2S gas and the functionalyzed surfactants, Zn(AOT)(2) and Cd(AOT)(2) Bis(2-ethylhexyl) sulfosuccinic acid formed as by-product restrains the formation of ZnS particles, and destabilizes the CdS particles. Neutralization of the acid by addition of an alkaline reagent, triisooctylamine, improves the conversion for ZnS particles and the stability for CdS particles, Ultrafine ZnS and CdS particles containing about 0.02 M of constituting ions are successfully prepared in the presence of the amine, The particles can be recovered from the reverse micelles and redispersed in non-micellar solvent via the surface capping of the particles with thiols. The proposed route using reverse micelles is applicable for the practical production of ultrafine particles.