The power-law distributions in molecular weights are found in the emulsion-polymerized polyethylenes, where the polymer transfer reactions are significant. A simple kinetic model for interval II in emulsion polymerization can describe the polyethylene distribution reasonably well, and this model is used to investigate the molecular weight distribution (MWD) formed in emulsion polymerization that involves chain transfer to polymer. The MWD profiles are dominated by the P-b value, which represents the probability that the chain end is connected, and by increasing P-b, the MWD changes from the exponential to the power-law distribution. A scale-free power-law distribution is formed for P-b > 0.5.