Bathymetric data were collected over all boatable areas of Upper Klamath and Agency Lakes, located in South-Central Oregon, in May and June of 1996. Areas that were too shallow (less than 1.2m) and/or covered with aquatic vegetation were not mapped. A 21ft tunnel-hull boat was fitted with an adjustable transducer mount on the stern. The transducer was mounted on the starboard side of the prop to minimize prop noise interference. A global positioning system (GPS) "rover" receiver's antennae mast was mounted directly above the transducer and connected to a Trimble 4000 GPS receiver. Differential correction updates were provided to the Trimble receiver at 1 second intervals from an OmniStar (John Chance Co., Houston, Texas) real-time GPS base station network. Shoreline data were collected by Klamath Tribes' staff. They drove adjacent to the shoreline in a shallow-draft inflatable boat that was fitted with a GPS data collector. These data were post-processed and shifted to match the boat-to-shoreline distance for specific segments. Depth data were collected with a Marimatech digital echosounder fitted with a 208khz transducer. The GPS system could not produce vertical positions accurate enough for the project. Accordingly, bottom surface elevations were determined by subtracting the sounded depth from the water surface elevation. Water surface elevations were calculated for each line of data collected via distance-weighted averaging of the two closest stage gage readings. Stage gages used for this project were located at Klamath Falls, Rocky Point, Rattlesnake Point, and on the north-central shore of Upper Klamath Lake, just west of the Williamson River confluence. The latter gage was a temporary pressure transducer arrangement installed specifically for this project. A level loop was run from U.S. Bureau of Reclamation control points to establish the datum elevation for this gage. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.