The occurrence of cellulase enzyme activity was examined in the stomachs of Texas fishes representing 26 species. Comparison ofthe results obtained from enzyme studies with food habits indicated that the two were independent. A hypothesis that the presence of certain enzymes might be correlated with black peritoneum in fish (McAllister 1959) must be rejected with regard to cellulase based on the results of this study. Unlike a previous study (Stickney and Shumway 1974) in which cellulase activity within species was always either present or absent, seven species examined during the present study were found to exhibit intraspecific differences in cellulase activity. Suggestions for further studies aimed at clarifying the mechanisms of cellulase occurrence and its potential importance to cultured species of fishes are presented.