Apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like (APOBEC) proteins are members of a protein family sharing the common characteristic of cytidine deaminase activity. The antiviral activity of APOBEC3G and APOBEC3F has been studied more extensively than that of the other members of this family. The antiviral activity of APOBEC3B and APOBEC3DE has also been described. Studies of other APOBEC proteins have not revealed any antiviral activities against HIV-1; however, further investigation is required. In the absence of human immunodeficiency virus type 1 (HIV-1) virion infectivity factor (Vif), APOBEC3G and APOBEC3F are incorporated into HIV-1 virions and hypermutate the viral genomic DNA by their cytidine deaminase activity. HIV-1 Vif protein suppresses the antiviral role of APOBEC proteins by several mechanisms that lead to inhibition of incorporation of APOBEC3G/3F into HIV-1 virions. The detailed mechanisms involved in the suppression of APOBEC proteins by Vif are still being elucidated. Novel studies in which as yet undefined aspects of the suppression of APOBEC proteins are investigated could reveal important and potentially exploitable information for addressing HIV-1 infection in humans.