Chondrocytes are the resident cells of cartilage. They are large, rounded cells derived from chondroblasts and are responsible for the synthesis of a series of collagenous and non-collagenous macromolecules of the extracellular matrix. These include type II collagen, aggrecan, linker protein, type IX collagen and type XI collagen. The control of chondrogenic cell proliferation and differentiation is essential for the coordinated development of the vertebrate skeleton. Chondrocytes are able to produce and respond to a large number of peptide growth factors and cytokines, including insulin-like growth factor-1 and interleukin-1. Chondrocyte cultures are useful in vitro models for studying cartilage regeneration and repair, the effects of cytokines and growth factors on cartilage, the regulation of specific genes and the pathophysiology of arthritis.