The cytopathic effect of HIV on CD4 T cells, as well as the active autoimmune mechanism occurring during infection, have been documented. Of the cytokines involved in the pathogenesis of AIDS, the main one produced by the monocyte-macrophage series is tumor necrosis factor alfa (TNF alpha). This cytokine induces antigens such as proteinase 3 (Pr 3) or mieloperoxidase (MPO). Anti-neutrophil cytoplasmic antibodies (ANCA) are directed against this type of PMN antigens. In the present paper, the role of anti-neutrophil cytoplasmic antibodies (ANCA) in HIV infected patients as responsible for autoimmune phenomena in relation to opportunistic infections, was studied. A total of 88 serum samples belonging to 49 asymptomatic and 39 symptomatic HIV infected patients were tested for ANCA by an indirect immunofluorescence (IIF) test over a neutrophil substrate. ANCA were detected in 53.8% of symptomatic patients as compared to 4.1% in asymptomatic cases (p < 0.0001). A 95.9% correlation was observed between ANCA-positive samples and pulmonary infection (n = 20). In those ANCA (+) samples 95.9% correlation was found with pulmonary infection (n = 20). Pulmonary infection due to Mycobacterium tuberculosis is a frequent finding in HIV infected patients from Northeastern Argentina. When the presence of ANCA in TB(+) HIV(+) and TB(+) HIV(-) patients was studied, it was seen that positive-ANCA significantly correlated with the first group (p < 0.001). The presence of ANCA was not related to viral infections, toxoplasmosis, neurological features of AIDS, vasculitis or malignant diseases. ANCA during pulmonary infection, mostly caused by TB, as well as PMN infiltration in pulmonary parenchyma, and the deregulated immune reaction elicited by HIV, may contribute to the onset of autoimmune phenomena. The presence of human T lymphocytes reactive to heat stress proteins (Hsp), an important target of immune response against certain intracellular auto-antigens such as MPO from PMN, added to the mechanism of molecular mimicry, could explain the association of ANCA and TB in patients with severe alterations of their immune response. According to these results, the limited presence of ANCA in asymptomatic patients HIV(+) and in HIV(-) with pulmonar TB, could indicate that the virus may not be responsible for the induction of these antibodies.