Recent biological studies and structural analyses have shown a pivotal role of homo- and hetero-oligomerization of G-protein coupled receptors (GPCRs) in physiological conditions and disorders. These studies were performed mostly by structural biology using X-ray and BRET analyses. There is the limitation in these methods for the elucidation of the native state of dimeric receptors in living cells because of the conformational or functional changes due to the mutations. Development of bivalent ligands of GPCRs brings us to estimate the precise distance between dimeric receptors and have advantages in binding affinity and specificity. However, ample challenges in design of bivalent ligands have showed its difficulty due to the unclearness of GPCR dimeric forms. Therefore, there is an increasing demand for a novel strategy for this analysis. We have adopted CXCR4, which belongs to the chemokine receptor family, as an example of GPCRs because we have developed its several potent antagonists such as 14-mer peptide T140 derivatives (phase III clinical trial) and a cyclic pentapeptide FC131 [cyclo(-D-Tyr-Arg-Arg-Nal-Gly-)] (Nal = L-3-(2-naphthyl)alanine), and designed and synthesized novel bivalent CXCR4 ligands with two FC131 analogues connected by a polyproline or a PEGylated polyproline linker. The linkers were expected to sustain a certain constant distance between the ligands. The bivalent ligands with suitable lengths of polyproline linkers have remarkably higher binding affinity compared to monomeric ligands, and enable to measure the distance between two binding sites of ligands in CXCR4 dimers. Fluorescent-labeled bivalent ligands have become useful bio-probes for the detection of cancerous cells with overexpression of CXCR4. In addition, bivalent ligands based on T140 derivatives have been synthesized to produce effective cancer metastatic inhibition with the therapeutic potential. Taken together, these advantages of bivalent GPCR ligands will be introduced in this symposium.