Historical records and natural history collections have been used as important tools to determine the status of populations. The objectives of this project were to compile a list of the fishes that have inhabited Triplett Creek and to identify changes in the fish assemblage in Triplett Creek. Historical records and vouchered specimens document 80 species from 19 families in the Triplett Creek system between 1890 and 1998. In a survey of the Triplett Creek system in 1999 and 2000, 16,554 specimens were collected, representing 54 species from 11 families. At least 3 fish species are considered extirpated from Triplett Creek, and 3 new fish species [Gambusia affinis (western mosquitofish), Moxostoma macrolepidotum (shorthead redhorse), Percina copelandi (channel darter)] were collected. A comparison of 3 collecting periods using Jaccard's Coefficient of Community Similarity (CC) indicates that the fish assemblages are similar (pre-1950 vs. 1950-1998 CC=0.77; pre-1950 vs. 1999-2000 CC=0.66; 1950-1998 vs. 1999-2000 CC=0.69). Differences in collecting methods and intensity were considered important factors limiting the detection of changes in the fish assemblage.