A continuous-flow, backmix reactor, based upon the principle of drag flow and capable of handling viscous reactions, was designed and constructed. Its backmixing effectiveness was demonstrated via residence time distribution measurements, flow visualization experiments, and a stepwise polymerization reaction. The molecular weight distribution of the resulting polymer, which was measured and contrasted with that produced in a plug-flow type [extruder] reactor, was significantly altered by backmixing, as predicted computationally.