The balance between osteoblast-dependent bone formation and osteoclast-dependent bone resorption maintains bone homeostasis. In inflammatory conditions, this balance shifts toward bone resorption, causing osteolytic bone lesions observed in rheumatoid arthritis and periodontitis. A recently discovered family of cytokine IL-17 is widely reported to mediate diverse inflammatory processes. During the last decade, novel roles for IL-17 in skeletal homeostasis have been discovered indicating the potential importance of this cytokine in bone metabolism. This review will summarize and discuss the involvement of IL-17 during bone homeostasis in both physiologic and pathologic conditions. A better understanding of the role of IL-17 in skeletal systems warrants an advance in bone biology, as well as development of therapeutic strategies against bone-lytic diseases, such as rheumatoid arthritis and periodontitis.