The template-fixed &bgr；-hairpin peptidomimetics Cyclo(-Tyr-His-X-Cys-Ser-Ala-DPro-Dab-Arg-Tyr-Cys-Tyr-Gln-Lys-DPro-Pro), disulfide bond between Cys4 and Cys11, and pharmaceutically acceptable salts thereof, with X being Ala or Tyr, have CXCR4 antagonizing properties and can be used for preventing HIV infections in healthy individuals or for slowing and halting viral progression in infected patients； or where cancer is mediated or resulting from CXCR4 receptor activity； or where immunological diseases are mediated or resulting from CXCR4 receptor activity； or for treating immuno suppression； or for treating inflammation, or, in particular, for stem cell mobilization of peripheral blood stem cells and/or mesenchymal stem cell (MSC) and/or other stem cells which retention depend on the CXCR4-receptor.
