The invention provides a variety of therapeutic uses for CXCR4 antagonists. In various embodiments, CXCR4 antagonists may be used as therapeutically as follows, or to manufacture a medicament for such therapeutic treatments: reducing interferon gamma production by T-cells, treatment of an autoimmune disease, treatment multiple sclerosis, treatment of cancer, inhibition of angiogenesis. The invention provides corresponding methods of medical treatment, in which a therapeutic dose of a CXCR4 antagonist is administered in a pharmacologically acceptable formulation. Accordingly, the invention also provides therapeutic compositions comprising a CXCR4 antagonist and a pharmacologically acceptable excipient or carrier. The CXCR4 antagonists for use in the invention may be peptide compounds comprising a substantially purified peptide fragment, modified fragment, analogue or pharmacologically acceptable salt of SDF-1.