The interfacial polycondensations of nylon 66 in a continuous reaction system have been studied. An experimental stirred flow reactor was used to determine both yield and intrinsic viscosity (molecular weight) as functions of reactant ratio (adipoyl chloride/hexamethylene-diamine), and Reynolds number from laminar to turbulent flow. It was found that mass transfer was the controlling factor in the reaction system. The yield as a function of Reynolds number was found to directly correlate with the behavior of the combination of mass transfer coefficient and interfacial area. Intrinsic viscosity had maximum values in the same reactant ratio range as for batch and continuous cascade systems studied earlier. Intrinsic viscosity behavior was shown to relate to interfacial area behavior.