The problem of cartilage breakdown in rheumatoid arthritis can partially be studied using in vitro techniques. Among the numerous models, organoid (high density) cultures have proved to be quite suited for these purposes. Chondroblasts/chondrocytes, obtained by cultivating precartilage cells of limb buds from day-12 mouse embryos, were cocultivated with mouse peritoneal macrophages in high-density or monolayer cultures. The result was an extensive breakdown of the cartilage matrix. Numerous chondrocytes detached from the matrix and became fibroblast-like cells. Immunomorphological methods showed that collagen type II, fibronectin and several integrins (beta 1-, alpha 3-, and alpha 5 beta 1 types) disappeared from the surface of chondrocytes. These pathological findings in cartilage tissue could be due to degradative products of macrophages and also chondrocytes. The in vitro model introduced here should be useful for studying matrix components and the turnover of matrix receptors of cartilage tissue in vivo under pathological conditions.