This investigation aimed to identify the behaviour of primate mandibular condylar cartilage cells in an in vitro model. Cells were harvested from the mandibular condyles of 1-year-old marmosets and maintained in primary culture for up to 30 d. Cell proliferation, structure, and phenotype were assessed at regular intervals by phase-contrast microscopy, cytologic staining, and immunocytochemistry. Cell growth increased progressively, and cultures reached confluence after 22 d. Cells were initially small and round but later became enlarged and heterogeneous in shape. Polygonal and hypertrophic chondroblast-like cells dominated the mature cultures. Glycosaminoglycan synthesis increased as cultures aged. Type I collagen was produced by early cultures, whereas type II collagen predominated in mature confluent monolayers. It is suggested that this mixed population of cells underwent phenotypic changes in primary cell culture that closely resemble the normal in vivo maturation process.