The Master Water Data Index of the U.S. Geological Survey contains records and information for 13,925 ground-water quality collection sites in Florida as follows: 2,180 active and 11,559 inactive well sites, and 39 active and 147 inactive spring sites. Ground-water quality data have been and are being collected at more sites in Florida than are other types of ground- and surface-water hydrologic data. Information available from the Master Water Data Index includes location (county, hydrologic unit, and latitude-longitude); reporting agency; agency identifying number; period and frequency of record; types of data (parameter sampled); and for wells, the principal aquifer sampled and well depth. This information may be retrieved, upon request, in a variety of formats. This report contains an index of the information available, not the actual water-quality data itself. The actual data may be obtained from the reporting agency that collected and stored the data. (USGS)