A novel procedure for the production of polymer latex in a flow tubular reactor capable of achieving high solids content latex (>30 wt %) is reported herein. The novelty of this approach consists of using a biphasic solution-aqueous phase containing polymer seed and a pure monomer organic phase-without pre-emulsification and feeding this solution slowly in a heated tubular reactor (slug flow). The polymerization was conducted over multiple stages to allow the addition of precise quantities of surfactant. The surfactant loading needed for stabilization-without causing secondary nucleation-was determined as a function of the latex particles' sizes through a series of batch experiments. Using this multistage polymerization strategy, poly(methyl methacrylate) latexes with a solids content of 35 wt % (131 nm) were successfully produced with no noticeable fouling of the reactor.