Storage of natural gas in salt caverns had been developed mainly for seasonal storage, resulting in a small number of yearly pressure cycles and moderate gas-production rates. The needs of energy traders are changing toward more aggressive operational modes. The "high-frequency cycling" operation of salt caverns raises questions concerning the effects of frequently repeated and extreme mechanical and thermal loading. These questions concern the constitutive creep laws for salt, laboratory test procedures, criteria to be used at the design stage to provide operability, and the long-term integrity of the underground salt caverns.