Water resources data for the 1977 water year for Mississippi consist of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; and water levels of wells. This report contains discharge records for 85 gaging stations; stage records for 15 of these gaging stations; stage only for 3 gaging stations; contents for 4 lakes; water quality for 25 gaging stations, 2 partial-record stations, and 169 wells; and water levels for 186 observation wells. Also included are data for 138 crest-stage partial-record stations. Additional water data were collected at various sites, not part of the systematic data collection program, and are published as miscellaneous measurements. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Mississippi.