Recurrent aphthous stomatitis (RAS) is a chronic condition, usually with a childhood or adolescent onset and with a tendency to diminish in frequency and severity with age. Most patients are otherwise healthy. The differential diagnosis for “aphthae” includes vesiculobullous diseases, granulomas, and even squamous cell carcinomas. The onset of aphthous‐like lesions in adults suggests the possibility of developing a more complex systemic disorder such as Behcet's syndrome or inflammatory bowel disease. Treatment includes correction of underlying diseases or predisposing causes, and the use of topical and systemic anti‐inflammatory agents or immunomodulating drugs.