The opportunistic behavior and the potential interactions of human herpesvirus 7 (HHV-7) with human immunodeficiency virus (HIV)-1 in HIV-1-infected patients were investigated in comparison with HHV-6, another human roseolovirus. Roseolovirus DNAs were detected and quantified in peripheral blood mononuclear cells (PBMCs) from 198 HIV-seronegative healthy blood donors, 38 HIV-1-infected patients classified as long-term non-progressors, and 99 HIV-1-infected patients classified as progressors. The rate of HHV-7 DNA detection was higher in healthy donors (78%) than in long-term non-progressors (47%; P = 0.0003) or in progressors (52%; P < 0.0001). HHV-7 cell load was higher in healthy donors (median: 212 EqCop/106 PBMCs) and in long-term non-progressors (median: 105 EqCop/106 PBMCs) than in progressors (median: 48 EqCop/106 PBMCs; P < 0.0001 and P = 0.015, respectively). Among progressors, HHV-7 detection was correlated positively with the CD4+ T-lymphocyte count (P = 0.028). Neither HHV-7 detection rate nor cell load was correlated with the HIV-1 plasma load. As a whole, HHV-6 detection rate and cell load were lower than the HHV-7 counterparts, albeit exhibiting similar differences between healthy donors, long-term non-progressors, and progressors. In conclusion, HHV-7 infection does not appear to be stimulated by HIV-1 infection, nor interact with it. Rather, HHV-7 detection rate and cell load reflect CD4+ T-lymphocyte count, with higher values in healthy donors and long-term non-progressors than in progressors. J. Med. Virol. 76:223–228, 2005. © 2005 Wiley-Liss, Inc.