Abstract: Oral submucous fibrosis is a chronic debilitating disease of oral mucosa and is characterized by generalized fibrosis of the oral soft tissues which tends to present itself clinically as palpable vertical fibrous bands. Traditionally, stains such as van- Geison and various forms of trichrome have been used to detect collagen fibres in tissues. Thick and thin collagen fibres play a vital role in maintaining connective tissue integrity. However, both these stains fail to reveal thin collagen fibres. A special stain- picrosirius red stain (PSR) that stained both thin and thick collagen fibres was used in this study. Thus, the present study is to demonstrate the orientation and color of collagen fibres in different grades of oral sub mucous fibrosis and normal mucosa and observed under polarized microscope. However, correlation to the grading of OSF will help in determining the changes in the connective tissue which precedes the neoplastic change in epithelium.