The cellular and collagenous components of the bovine temporomandibular joint (TMJ) disc have been isolated and analysed. In the central regions of the disc, significant amounts of type I, II, IX and XII collagen were found. The identity of these molecules was verified with collagenase digestions, Western blot analysis and Northern blot analysis (for type II collagen). Cells isolated from the TMJ disc synthesized alkaline phosphatase, proteoglycans and collagen in culture; however, the basal rate of synthesis for these molecules was lower than that for isolated osteoblasts, articular and growthplate chondrocytes. The TMJ disc cells proliferated more rapidly in culture than osteoblasts or chondrocytes. Transforming growth factor-beta stimulated proliferation by 250%, whereas prostaglandin E2 had no effect.