The mobilities of several mass-identified positive ions in helium, neon, and argon buffer gases were measured in a flow drift tube apparatus as a function of E/N at 297 K. The systems studied were N2O+, NO2+, and SO2+ in He, H2O+, O2+, and N2O+ in Ne, and H2O+, H3O+, N2O+, NO2+, and SO2+ in Ar. The values obtained were compared to previous measurements and Langevin mobilities and were used to estimate the well depth of the ion buffer interaction potential.