Trace elements (Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl) were determined in muscle (fillet) of average sized fish (mostly carp, catfish, and sucker) collected from the confluences of major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG). Also, trace elements were determined in fish from reservoirs upstream (Abiquiu [AR]) and downstream (Cochiti [CR]) of LANL from 1991 through 1999. In general, all of the (mean) trace elements, including Hg, were either at the limits of detection (LOD) or in low concentrations at all study sites. Of the trace elements (e.g., Ba, Cu, and Hg) that were found to be above the LOD in fish muscle collected from LANL canyons/RG, none were in significantly higher (p < 0.05) concentrations than in muscle of fish collected from background locations. Mercury concentrations (mean of means) in fish from AR (all other trace elements were at LOD) were significantly higher (p < 0.10) than Hg concentrations in fish from CR, and Hg concentrations in fish collected from both reservoirs exhibited significantly (AR = p <0.05 and CR = p < 0.10) decreasing trends over time.