There are only few reports on the correlation between bacterial products and the GAG pattern of cartilage. Mycobacteria bovis (BCG) were applied to chondrocyte monolayer cultures for one week. The following parameters did change: cell proliferation increased, glycosaminoglycan synthesis and secretion decreased, hyaluronic acid in secreted and cell-associated glycosaminoglycans increased, a correlation between the degree of these changes and the degree of cell differentiation seems to exist. The contact of bacteria like BCG to chondrocytes may change the cellular metabolism. On the tissue level this may injure articular cartilage and thus support the concept of predamaged cartilage that is readily susceptible to further degradation.