Cellulases have enormous potential in industries and are used in food, beverages, textile, laundry, paper and pulp industries etc. Although a large number of microorganisms are capable of degrading cellulose, only a few of these microorganisms produce significant quantities of cell-free enzymes capable of completely hydrolysing crystalline cellulose in vitro. Fungi are the main cellulase-producing microorganisms, though a few bacteria and actinomycetes have also been recently reported to yield cellulase activity. Generally, fungi produces three major types of cellulolytic enzyme: endoglucanase, exoglucanase and B-glucosidase. These enzymes are extracellular and inductive in nature. The ability to produce cellulase are widespread among fungi and this has became the subject of extensive investigation. The research work explained in this book was intended to screen the cellulolytic ability of fungi isolated from soil contaminated with effluents of cotton ginning mills. Furthermore, optimal condition for enzyme production and purification were also explained in this book.