The U.S. Geological Survey (USGS), in cooperation with Federal, State, and local agencies, obtains a large amount of data on the water resources of the State of Florida each water year. These data, accumulated during many water years, constitute a valuable database that is used by water-resources managers, emergency-management officials, and many others to develop an improved understanding of water resources within the State. This report series for the 2002 water year for the state of Florida consists of records for continuous or daily discharge for 392 streams, periodic discharge for 15 streams, continuous or daily stage for 191 streams, periodic stage for 13 streams, peak stage and discharge for 33 streams, continuous or daily elevations for 14 lakes, periodic elevations for 49 lakes, continuous ground-water levels for 418 wells, periodic ground-water levels for 1,287 wells, and quality-of-water for 116 surface-water sites and 291 wells. This volume (Volume 4, Northwest Florida)contains records of continuous or daily discharge for 67 streams, periodic discharge for 1 stream, continuous or daily stage for 16 streams, periodic stage for 1 stream, peak stage and discharge for 29 streams, continuous or daily elevations for 1 lake, periodic elevations for 3 lakes, continuous ground-water levels for 2 wells, periodic ground-water levels for 3 wells, and quality-of-water for 5 surface-water sites and 0 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, State, and Federal agencies in Florida.