The 40 wt % solids content styrene/butyl acrylate miniemulsion photopolymerization was successfully carried out in a continuous tubular reactor. The effect of the type and concentration of photoinitiator (PI), the incident light irradiance (ILI), and the residence time on polymerization kinetics and polymer microstructure was investigated. An optimal value for the ILI that maximizes monomer conversion was found. The shape of the molecular weight distribution (monomodal versus bimodal) can be varied by modifying the particle size and the type of photoinitiator.