Underground gas storage is the practical means of making available the increased supplies of natural gas that are needed in Indiana in winter periods of peak demand. To date, 21 gas storage projects providing an estimated storage capacity of 48 billion cubic feet have been initiated. Expansion of storage capacity is anticipated. Basic geologic factors and availability of subsurface information make establishment of gas storage in the Illinois Basin much easier than in the Michigan Basin or on the Cincinnati Arch. Within the Illinois Basin, storage possibilities are good in the area in which Pennsylvanian and Mississippian rocks contain oil and gas and are excellent in the Geneva Dolomite belt. Throughout Indiana reservoir conditions in Ordovician and Cambrian rocks are adequate for gas storage, but known significant entrapments in these rocks are few.