Recurrent Aphthous Stomatitis (RAS) is a widely prevalent inflammatory condition manifesting as recurrent, single or multiple, shallow ,well-defined ,round or oval , painful ulcers in the oral mucosa The three clinical forms of RAS are minor, major and herpetiform types, among which  minor RAS is the most common variant. Multiple factors such as genetic predisposition, immunological abnormalities, nutritional deficiencies, infective agents, allergies, stress and local trauma have been implicated in the etiology of RAS.   Abnormal expression of pro-inflammatory cytokines including tumor necrosis factor- alpha (TNF- α) in the oral mucosa plays a crucial role in etiopathogenesis of RAS as it increases cellular immune response in focal areas of the oral mucosa. TNF α production can be inhibited by Vitamin D, a multifunctional lipid-soluble hormone which has gained attention for its immunomodulatory functions by regulation and modulation of innate and acquired immune responses.  Numerous studies have identified significantly reduced serum vitamin D levels in subjects with RAS and thus supplementation of oral vitamin D3 has been proposed as a safe promising intervention for the treatment of RAS subjects with low serum vitamin D levels. However, it is uncertain whether supplementation with vitamin D3 would benefit all persons with RAS. Since there are few studies pertaining to supplementation of oral Vitamin D3 in RAS, the present study aims to assess the effectiveness of oral Vitamin D3 supplementation on the clinical parameters and serum TNF α levels in subjects with minor RAS.