Three Native American children with severe combined immunodeficiency developed noma, a necrotizing gingivostomatitis not previously reported in this country. The similarity between the clinical findings and those observed in monkeys with simian AIDS prompted us to evaluate our patients and their families for human retroviral infection. Antibodies to HTLV-I or HTLV-III/LAV proteins were not identified in patients nor in their family members. Standard bacterial and viral cultures similarly failed to identify a suspect pathogen.