This report summarizes water-resources investigations in the Southwest Florida Water Management District performed by the U.S. Geological Survey, Water Resources Division, for fiscal year 1978. The investigations are part of the Federal program of appraising the nation 's water resources. The cooperative program for fiscal year 1978 included 37 interpretive investigations. Abstracts of 30 reports released during 1978 and a bibliography of reports released since 1933 are included. The hydrologic setting of southwest Florida and discussions of surface-water, ground-water, and quality-of-water conditions are given. Hydrologic conditions in southwest Florida are described and illustrated by hydrographs of selected surface-water, ground-water and lake-stage data collection sites. In addition, summaries of water-use data and data on the regional observation monitor-well program are provided. (Kosco-USGS)