Human immunodeficiency virus (HIV) infection is associated, like allergic diseases, with altered T cell regulation. Total serum IgE levels were measured in 65 infected patients. The mean IgE level of subjects with a T lymphocytes number < or = 200/mmc was greater than mean IgE level of subjects with a T cell number > 200/mmc. No prevalence of atopic diseases was noted in the two groups. The elevation of IgE may be related to a difference in IgE regulatory lymphokines produced by T lymphocytes.