Growth of endochondral bones is regulated by the coordinated proliferation and differentiation of chondrocytes in the epiphyseal growth plates. Many skeletal diseases are caused by pathogenic disruptions of these two processes. While the intracellular mechanisms regulating chondrocyte proliferation and differentiation are poorly understood, recent evidence from studies using genetically altered mice and from experiments in cultured chondrocytes point to a prominent role of cell cycle proteins in this context. This article summarizes our current understanding of the expression, regulation, and function of cell cycle genes in chondrocytes.