Defining the trophic position of stream organisms is a first step in understanding the ecology of lotic systems. Whereas trophic positions of stream fishes have been traditionally assigned based on dietary analysis, stable isotope ratios may provide additional information on the validity of this approach and may be used to verify energy acquisition assumed from dietary studies. In this study, we assessed the concordance of literature-based trophic classifications and isotopic δ¹⁵N signatures for small-bodied fishes from four streams in Kansas, Oklahoma and New Mexico. ANOVA results revealed no significant difference (F_2,27 = 1.71, P = 0.201) in trophic position based on δ¹⁵N values among three broad trophic classifications derived from literature sources (algivores/detritivores, omnivores and invertivores). Both the prevalence of omnivory in stream fishes and potential biases associated with isotope fractionation at different trophic levels poses potential problems when classifying lotic fish into trophic positions.