Interaction between herpesviruses and human immunodeficiency virus (HIV)1 is postulated in the progression of HIV disease. In order to evaluate the specific antibody responses directed to Epstein-Barr virus (EBV) and cytomegalovirus (CMV) and to provide serological evidence suggesting reactivation of these viruses able to accelerate the immunodeficiency, we studied IgA and IgG titres to EBV and CMV in the serum of HIV positive patients in relation to the CD4 cell number. The titres of IgG antibodies to EBV and the prevalence of IgG to CMV were significantly higher in HIV positive patients compared to control high risk HIV negative subjects. In HIV infected patients, anti-VCA IgG antibodies increased and anti-EBNA IgG antibodies decreased progressively in relation to the decline of CD4 cell number whereas anti-CMV IgG antibodies did not varied significantly at the same time. Anti-VCA IgA and anti-EA IgG antibodies were found uncommonly and with low titres. IgA antibodies to EA and CMV were not detected in any patient. The variations in EBV antibody response that we describe in HIV infection were previously reported in other immunodeficiency states and could be distinctive of these diseases.