This preliminary report on the natural brines of Indiana and adjoining parts of Illinois and Kentucky is a compilation of 473 brine analyses. The analyses were obtained from the files of many companies as well as from published reports of the Indiana, Illinois, and Kentucky Geological Surveys. The analyses are classified on a stratigraphic basis and cover stratigraphic units that range from the Knox Dolomite (Cambrian and Ordovician Systems) to the Pennsylvanian System. The locations of wells or leases from which samples were obtained for 11 units of the Chester Series and the Ste. Genevieve Limestone (Mississippian System) are shown on maps. The total solids in parts per million of the brines sampled from these stratigraphic units also are shown on the maps. A comprehensive brine-analysis program has been started by the Indiana Geological Survey. This program will result in a relatively detailed publication on Indiana brines.