[(Cys(Bzl)84,Glu(OBzl)85)]CD4 (81-92) is a selective inhibitor of HIV-1. [(Cys(Bzl)84,Glu(OBzl)85)]CD4 (81-92) inhibits viral infection and cell fusion by blocking the interaction between HIV-1 and CD4 molecules. [(Cys(Bzl)84,Glu(OBzl)85)]CD4 (81-92)can completely inhibit fusion formation at a concentration of 25 μM.