Abstract: In the present study, twenty-three strains of Piromyces sp. obtained from ruminants and non-ruminants were grown in Medium 10 in the presence of paddy straw as the sole source of fermentable carbon. The activity of extra-cellular fibrolytic enzymes such as avicelase, filter paper cellulase, β 1, 4 endoglucanase, β glucosidase and acetyl esterase were estimated in the various axenic cultures. The activity of the exoglucanase on avicel (avicelase activity) and filter paper was found to be significantly higher (P<0.05) in the Piromyces strains isolated from Nilghai, the Indian elephant and the camel. In the four strains of the Piromyces isolated from the domestic ruminants, the activity of the exoglucanase on avicel (avicelase activity) and filter paper was found to be the lowest as compared to all other strains of Piromyces isolated from the wild herbivores, camel/horse (< 4.0 µmoles/mg protein).