Monitoring of the Pend Oreille River from 2001 through 2004 at the Idaho state line near Newport, and in the forebays and tailraces of Box Canyon and Boundary Dams, shows that total dissolved gas (TDG) frequently exceeds water quality standards. As a result, the Washington State Department of Ecology (Ecology) listed the Pend Oreille River on its 2004 303(d) list of impaired waters and has determined the Total Maximum Daily Load (TMDL) for TDG in the Pend Oreille River. The U.S. Environmental Protection Agency is issuing a TMDL for the section of the Pend Oreille River that flows through the reservation of the Kalispel Tribe of Indians. Ecology is issuing this TMDL for the Pend Oreille River in Washington State, other than the section flowing through the reservation. Total dissolved gas was monitored in the Pend Oreille River with datalogging and profiling multi-parameter instruments from March through July 2004 near Newport, Ruby, Box Canyon Dam, and Boundary Dam. Data show that TDG changes over time at these sites. These data also allow comparisons to data collected by other organizations.