In this study we describe a series of nine patients affected by acquired immunodeficiency syndrome (AIDS) or AIDS-related complex who had hypereosinophilia and hyperimmunoglobulinemia E (hyper-IgE) with chronic dermatitis and recurrent staphylococcal infections. These patients had features similar to those present in hyper-IgE syndrome, a primary immunodeficiency disease. In addition, immunologic characterization of these patients with human immunodeficiency virus (HIV) infection, compared with 51 HIV-positive patients without hyper-IgE, both atopic and nonatopic, and three patients affected by the primary hyper-IgE syndrome, also revealed an increase in IgA and a severe decrease in B and CD4+ lymphocytes. Spontaneous in vitro synthesis of IgE by peripheral blood mononuclear cells was confirmed in both hyper-IgE conditions, together with increased levels of circulating eosinophil cationic protein. Serum-soluble CD23, usually increased in atopic conditions and hyper-IgE, was similar to that of normal control subjects in the HIV-positive patients with hyper-IgE. On the basis of our findings, we conclude that a hyper-IgE-like syndrome represents a distinct aspect of the clinical manifestations associated with HIV infection and that the immunologic mechanisms in this condition seem to differ from those known in primary hyper-IgE syndrome, because CD4+ TH2 type cells, which are currently believed to have a role in IgE production, are severely depleted in HIV-positive patients.