To date, it has been generally assumed, based on early experimental work, that ATRP in aqueous dispersed systems is incompatible with anionic surfactants. In the present work, it is clarified that this incompatibility originates in the anionic surfactant (sodium dodecyl sulfate, SDS) displacing the halide ligand from the Cull bromide-based deactivator, converting it to a Cull complex, unable to deactivate radicals. This results in a very high polymerization rate as well as essentially no control over the molecular weight distribution. It is demonstrated how such loss of deactivator can be minimized by the addition of a source of halide ions, thus enabling one to conduct ATRP in aqueous dispersed systems using commonly available and inexpensive anionic surfactants such as SDS.