Laboratory measurements of the argon gas permeability for rock salt specimens from the Waste Isolation Pilot Plant (WIPP) site in Southeast New Mexico (SENM) are obtained by using a transient, pressure-step technique. Hydrostatic and differential pressure states are investigated as a function of confining pressure and time. These data, when combined with the results of other experimenters, lead to the conclusions that the in-situ permeability of the undisturbed formation is less than 0.05 ..mu..d; the introduction of non-lithostatic stress states into the formation, as with mining, may produce connected porosity that will increase the permeability of the formation; and, hydrostatic pressure states applied for finite time periods tend to heal the formation to its original undisturbed state.