BACKGROUND: Saliva is a complex fluid, which influences oral health through specific and nonspecific physical and chemical properties.Saliva plays a major role in maintaining the neutrality of the pH in oral cavity. Alterations in salivary pH and flow can be affected by various pathological and physiological conditions.Hence determining the pH at the local site is essential to know the progression of the condition.Oral leukoplakia is defined as essentially an oral mucosal white lesion that cannot be considered as any other definable lesion with an increased risk of malignant transformation. Oral lichen planus (OLP) is a chronic mucocutaneous disorder of stratified squamous epithelium of uncertain etiology that affects oral and genital mucous membranes, skin, nails, and scalp. Recurrent aphthous ulcer is a self limiting painful mucosal condition which is often preceded by a prodromal burning sensation lasting for 24-48 hours.The management of such cases can be challenging,Hence determining the mucosal pH can be helpful as an Early Diagnostic Biomarker. Aim: To Compare mucosal pH in patients with Oral leukoplakia,Oral lichen planus and Recurrent aphthous ulcers with healthy individuals. Objectives: The purpose of this study has two aspects a) to determine the differences in mucosal pH in patients with Oral Leukoplakia,Oral Lichen planus and Recurrent aphthous ulcers and healthy individuals and b) if mucosal pH can be used as an early diagnostic biomarker. Materials and Methods: The study included pH strips to access mucosal pH in 20 Oral leukoplakia patients , 20 Oral Lichen Planus , 10 Recurrent aphthous Stomatitis and 20 Healthy individuals(controls). We are permitted to take subjects from the Department Of Oral Medicine And Radiology based on our inclusion and exclusion criteria and the subjects are explained about the study. The pH strip is wetted with the saliva and is compared with the standard pH index. Results: The analyzed data showed statistically significant differences in the mean pH of patients with OLP, OL and RAS patients when compared to that of the normal healthy controls. It also showed significant difference when all the subjects were compared with Gender and Age(p value = 0.0270 and 0.0029 respectively).In pairwise comparisons of RAS with OL and OLP there is a significant difference with p values 0.0034 and 0.0081 respectively. Comparison of 4 groups with mean pH showed a significant p value of 0.0142. Conclusion: Mucosal pH plays a significant role in maintaining equilibrium of oral health. Therefore, its alteration may indirectly affect the disease and its treatment outcomes.