Background and objectives: Oral submucous fibrosis is a well-recognized and most prevalent premalignant condition of oral mucosa in India and Southeast Asia. Frequent and prolonged chewing of tobacco exerts undue pressure on muscles of mastication, which in turn may result in work hypertrophy of muscle. The present study was undertaken to measure thickness of masseter muscle at rest and at clenching position by ultrasonography in oral submucous fibrosis patient and in control group, and also to establish the normal value of masseter muscle thickness ultrasonographically and to prove that ultrasonography is reliable diagnostic technique for the evaluation of masseter muscle hypertropy in oral submucous fibrosis patient. Materials and methods: Ultrasonographic measurements of masseter muscle thickness were performed using high frequency linear transducer for 45 subjects comprising of 30 oral submucous fibrosis patients and 15 controls. Results: Study group showed higher thickness both on right and left side masseter muscle and also in relaxed and contracted state when compared to controls. The thickness of masseter muscle is more in contracted state than relaxed state which was highly significant