The fish population in the heated discharge channel from Colbert Steam Plant on the Tennessee River was sampled from January 1972 to December 1973 to determine the effects of temperature on species composition, relative abundance, and diversity. Electrofishing (108 samples) and gill netting (36 samples) yielded a total of 34 species; median number of species per sample for each type ofgear was nine. Species that were commonly colleded from the discharge channel at maximum summer temperatures (33-35 C) included: spotted gar, gizzard and threadfin shad, carp, billegill, longear sunfish, spotted bass, largemouth bass, and channel catfish. The occurrence of only three species (skipjack herring, sanger, and walleye) was considered temperature dependent; these species apparently avoided the heated efHuent at temperatures above 30 C. Mortalities resulting from temperature differences were not ohserved. Regression analysis of two diversity indices computed for the electrofishing data indicated that species diversity was inversely related to temperature in the discharge channel (P < 0.05) but that the Shannon index (H) was not temperature dependent.