Despite the fact that the survival of people infected with human immunodeficiency virus (HIV) has improved worldwide because of the increasingly powerful and highly active antiretroviral therapy, opportunistic infections (OIs) of the central nervous system (CNS) remain a serious burden. HIV-1 is capable of entering the CNS through infected peripheral monocytes, but its effect on OIs of CNS remains unclear. In this study, we investigated the characteristics of HIV-1 in acquired immunodeficiency syndrome (AIDS) patients with CNS OIs. A total of 24 patients with CNS OIs and 16 non-CNS OIs (control) cases were selected. These AIDS patients were infected with HIV-1 by paid blood donors in China. HIV-1 loads in plasma and cerebrospinal fluid (CSF) were detected using RT-PCR, and the C2-V5 region of HIV-1 envelope gene was amplified from viral quasispecies isolated from CSF using nested PCR. The CSF HIV-1 load of CNS OIs was higher than that of non-CNS OIs, but plasma HIV-1 load of CNS OIs was not higher than that of non-CNS OIs. The nucleotide sequence of C2-V5 region of the HIV-1 quasispecies isolated from the CSF of CNS OIs had a high diversity, and the HIV-1 quasispecies isolated from the CSF of CNS OIs revealed R5 tropism as 11/25 charge rule. These results suggest that high levels of divergent HIV-1 quasispecies in the CNS probably contribute to opportunistic infections.