Oral submucous fibrosis (OSF) is a common pre-malignant condition of the mouth in arecanut chewers in Indian subcontinent. It is characterized by restriction in opening of the mouth, tongue protrusion, and cheek flexibility. Reports of muscle changes in OSF, using light microscopy are few. Incisional biopsy sections of thirty OSF patients were stained with Masson's Trichrome stain, to study the fibrosis involving the muscle. Wide spectrum of changes were observed where fibrosis was being evident sub-epithelially, not extending in to the muscle to cases where only a few remnants of muscle fibers were seen and the missing muscle bundle area being replaced by fibrous tissue. The probable mechanism by which these changes occur is discussed.