A total of 175 human immunodeficiency virus (HIV)-positive intravenous drug users (IDU) with CD4 cell counts of <200 cells/microl were matched with 175 HIV-positive IDU with CD4 cell counts of >500 cells/microl. Enzyme immunoassay (EIA) reactivity and human T-cell lymphotropic virus type 2 (HTLV-2) Western blot (WB) positivity were more frequently observed in subjects with CD4 cell counts of >500 cells/microl. Most of the subjects with low CD4 cell counts and EIA reactivity carried HTLV-2 infection (WB positive and/or PCR positive). No subjects with low CD4 cell counts and a lack of reactive EIA were PCR positive for HTLV-2. Therefore, a negative EIA result can confidently discharge HTLV-2 infection in HIV-infected patients with severe immunosuppression, whereas PCR should be performed for subjects with a reactive HTLV EIA which is not further confirmed by WB.