Recurrent aphthous stomatitis (RAS) is the most common oral mucosal disorder found in men and women of all ages, races, and geographic regions. There are three forms of the lesions (minor, major, and herpetiform), with major aphthous ulcers causing significant pain and potential for scarring. In HIV-infected individuals, these ulcers occur more frequently, last longer, and produce more painful symptoms than in immunocompetent persons. In addition, they may be associated with similar ulcerations involving the esophagus, rectum, anus, and genitals. The diagnosis of HIV-induced RAS requires a careful history of the condition, and a thorough extra- and intra-oral examination. Oral mucosal biopsies are required for non-healing ulcers in order to exclude the possibility of deep fungal infections, viral infections, and neoplasms. The cause of the ulcers in HIV-positive persons has not been elucidated--local diseases, genetic, immunologic, and infectious factors all probably play a role. The goals of current treatments are to promote ulcer healing, to reduce ulcer duration and pain while maintaining nutritional intake, and to prevent or diminish the frequency of recurrence. Initial therapy for infrequent RAS recurrences includes over-the-counter topical protective and analgesic products. Initial therapy for frequent RAS outbreaks requires topical anesthetics, binding agents, and corticosteroids. Major RAS and non-healing minor or herpetiform RAS may require intralesional corticosteroids and systemic prednisone. Second-line immunomodulators for frequent and non-healing ulcers includes thalidomide and other immunomodulators.