The fungus flora of cattle feeds, some of which had been associated with livestock disorders, was determined and compared to that of non-suspected cattle feeds. Most of these feeds were silages that had been preserved by the sodium metabisulphite method. Special techniques of isolation, including the use of a variety of natural and synthetic media, resulted in isolating 64 species of fungi, representing 3 classes, 7 orders, and 12 families. The formation of small, discrete colonies on malt salt agar allowed quantitative determinations of the number of colonies of fungi from dilutions of feed washings. Littman oxgall agar permitted the isolation of several species not isolated on the other media. Of the 64 species identified, 63 were obtained from sus -pected samples and 38 of these were isolated also from the non-suspected feeds. The following species, with known or suspected pathogenic or toxic abilities in livestock, were isolated: Mucor flavus, M. racemosus, Rhizopus arrhizus, R. nigricans, Haplosporangium decipiens, Candida albicans, C. humicola, C. krusei, Cryptococcus albidus, Aspergillus chevalieri A. flavus, A. fumigatus, A. nidulans, A. terreus, Monascus purpureus, Penicillium expansum, Chaetomium olivaceum, Cephalosporium kiliense, Paecilomyces variota, Scopulariopsis brevicaulis, Trichoderma koningi, Fusarium mohiliforme, Cladosporium herbarum, Pullularia pullulans, and Streptomyces spp.