The bicyclam AMD3100 (originally called JM3100), in which the two cyclam rings are tethered by an aromatic bridge, emanated from JM2763, where the two cyclam moieties are tethered by an aliphatic linker - JM2763 in turn originated from JM1657, where the cyclam rings are directly linked to one another via a C-C bridge, and which was identified as an impurity, showing anti-HIV activity, in a commercial cyclam preparation. AMD3100 proved very effective against HIV-1 and HIV-2, inhibiting virus replication within the nM range, without toxicity for the host cells at concentrations that were > 100,000-fold higher than those required to inhibit HIV replication. The anti-HIV activity of AMD3100 appeared to be confined to the Tlymphotropic (X4) HIV strains, i.e. those strains that use the CXCR4 receptor to enter their target cells, and AMD3100 as of today still stands as one of the most potent and selective CXCR4 antagonists ever discovered. Hence, AMD3100 was found to interfere with a number of (patho)physiological processes which depend on the interaction of CXCR4 with its natural ligand, stromal derived factor (SDF-1) and which play an important role in rheumatoid, allergic and malignant diseases. AMD3100 has been shown to mobilize CD34+ stem cells from the bone marrow into the bloodstream and has also been shown to augment migration of bone marrowderived endothelial progenitor cells into sites of neovascularization after myocardial infarction. Currently, AMD3100 is actively pursued as a stem cell mobilizer for transplantation in patients with multiple myeloma and non-Hodgkin's lymphoma.