The immunodeficiency state in HIV infected patients has been the cause of severe episodes of Recurrent Aphthous Stomatitis (RAS). Aim: Our study aims to establish correlation between the manifestations of RAS and the immunosuppression state caused by HIV infection, through counting of CD4+ cells, CD8+ cells, CD4+:CD8+ cells ratio and viral load. Study design: series study. Material and Method: Ninety-four HIV infected patients (25 women and 69 men) with RAS were evaluated in the ENT Department of the University of Sao Paulo-Medical School from January 1998 to December 2003. The age ranged between 19 and 63 years (mean = 35.3 years). The patients were divided in two groups: AIDS group and HIV infected group. Results: The patients with AIDS and HIV infection presented, respectively, eight ulcers and two ulcers by outbreaks. Similarly, patients with major RAS presented smaller counting of cells CD8+, CD4+ and CD4+/CD8+ cells, and higher mean value of viral load than the patients with herpetiform and minor RAS. Between patients with minor and herpetiform RAS there were no statistical differences. Conclusions: The emergence of the lesions, mainly in major RAS, is directly related to the immunological state of the HIV infected patient. These patients frequently present nutritional deficits and worsening in life style. Thus, diagnosis and treatment of RAS is a challenge that should not be neglected.