Receptor activator of NF-κB ligand (RANKL) and its receptor activator of NF-κB (BANK) play pivotal roles in osteoclast differentiation and function. However, the structural determinants of the RANK that mediate osteoclast formation and function have not been definitively identified. To address this issue, we developed a chimeric receptor approach that permits a structure/function study of the RANK cytoplasmic domain in osteoclasts. Using this approach, we examined the role of six RANK putative tumor necrosis factor receptor-associated factor-binding motifs (PTM) (PTM1, ILLMT-REE 286-293; PTM2, PSQPS349-353; PTM3, PFQEP 369-373; PTM4, VYVSQTSQE537-545; PTM5, PVQEET 559-564; and PTMG, PVQEQG604-609) in osteoclast formation and function. Our data revealed that the RANK cytoplasmic domain possesses three functional motifs (PFQEP369-373, PVQEET559-564, and PVQEQG604-609) capable of mediating osteoclast formation and function. Moreover, we demonstrated that these motifs play distinct roles in activating intracellular signaling. PFQEP369-373 initiates NF-κB, c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38 signaling pathways and PVQEET559-564 activates NF-κB and p38 pathways in osteoclasts, whereas PVQEQG604-609 is only capable of activating NF-κB pathway. Significantly, the revelation of these functional RANK cytoplasmic motifs has not only laid a foundation for further delineating RANK signaling pathways in osteoclasts, but, more importantly, these RANK motifs themselves represent potential therapeutic targets for bone disorders such as osteoporosis.