Oral squamous cell carcinoma (OSCC) is the most common malignancy of the oral cavity. Many times it is preceded by oral precancerous pathologies (OPP) namely leukoplakia, erythroplakia, and oral submucous fibrosis. The rate of malignant transformation is variable for these premalignant pathologies. Mast cells have a predominant role in tumor progression and metastasis. Mast cells contain proteolytic enzymes tryptase and chymase which is responsible for degradation of extracellular matrix. In the current research project, we have studied the comparative expression of mast cell tryptase activity in OSCC, OPP & NOM using immunohistochemistry method.