The recurrent aphthous ulcer (RAU) is a pathological change found in the oral mucosa, characterized by painful single or multiple ulcers. The etiologic aspect of RAU is not well understood; however it is known that due to lower CD4 cell counts patients had higher prevalence of these oral lesions, and immunosuppressed patients with HIV are predisposed. Patient FC is African descent, 26 years old, male, HIV + CD4 67 cells/mm(3), with minor RAU in the upper and lower right side lip, measuring about 4 mm, and major RAU in tongue and the tonsillar pillar measuring 2 cm. The patient was treated with laser therapy with the objective to help reverse the damage and decrease the symptoms. After one week there was remission of the lesions. The laser showed to be an important alternative therapy that promoted analgesic, healing effects and improving the quality of life of patients.