Expression of integrins, a family of cell adhesion proteins, by human articular cartilage chondrocytes in vivo has been studied by immunohistological techniques using cryostat sections and a panel of anti-integrin monoclonal antibodies. Chondrocytes strongly expressed β1 and α5 integrin subunits, known to form the classical fibronectin receptor, VLA-5, strongly. α1 was expressed more weakly and variably; α3 was expressed by occasional cells only. Chondrocytes did not express β2, β3 or other integrin α subunits tested.