Objectives: Bone disease is one of the hallmarks of multiple myeloma (MM). The role of osteoprotegerin (OPG) in the RANK/RANKL/OPG signaling system is well defined in the myeloma bone disease. Polymorphisms of the TNFRSF11B gene encoding OPG have been studied in various bone diseases. However, relationship between the levels of OPG and development of bone lesions regardless of RANKL is yet unknown. In this study, the effects of OPG gene polymorphism on the development of bone lesions in MM were investigated.