We evaluate radiation pressure from starlight on dust as a feedback mechanism instar-forming galaxies by comparing the luminosity and flux of star-forming systems to thedust Eddington limit. The linearLFIR–\hbox{$L_{\rm HCN}^\prime$}LHCN′ correlationprovides evidence that galaxies may be regulated by radiation pressure feedback. We showthat star-forming galaxies approach but do not dramatically exceed Eddington, but manysystems are significantly below Eddington, perhaps due to the “intermittency” of starformation. Better constraints on the dust-to-gas ratio and the CO- andHCN-to-H2 conversion factors are needed to make a definitive assessment ofradiation pressure as a feedback mechanism.