Oral sub-mucous fibrosis is a chronic, insidious, debilitating, precancerous condition affecting oral cavity, caused by the habitual use of areca nut. A variety of mediators determine the deposition of collagen that include hormones cytokines and lymphokines. Collagen fibres have been the main focus of study to understand the pathogenesis of the lesion. Picrosirius has the propensity to stain thin fibres also so it has been the most opted stain for study. The main aim of the study here is to compare and correlate the role of collagen fibres and their role in determining the transformation of Oral Submucous Fibrosis (OSMF) to Oral Squamous Cell Carcinoma (OSCC). A total of 40 formalin fixed paraffin embedded tissue (FFPE) blocks were retrieved from the department archives. They comprised of OSMF cases, cases of OSMF associated with OSCC and OSCC. Fresh sections were cut and stained with Picrosirius red to identify the collagen fibers. The content, pattern and distribution of collagen fibers were compared between the different groups. An observable change in stroma was evident as OSMF progressed to oral malignancy