The role of humoral immune mechanisms in the induction, maintenance, and modulation of chronic arthritis in the two main tissues of diarthrodial joints synovial membrane and cartilage is discussed. In the synovial membrane of patients with RA, the available data suggest that there is a selective enrichment of immunoglobulin-secreting cells with restricted specificities. However, it is likely that the B-lymphocyte lineages infiltrating the synovial membranes are not self supporting and autonomous but that they originate from precursors activated and released from the central lymphoid organs. The processes leading to irreversible destruction of articular cartilage in chronic arthritis are not well understood. A review of the possible pathogenic role of immunoglobulin and immune complexes tightly bound to the superficial layers of cartilage suggests that these contribute to the chronicity and severity of the inflammatory process. However, accurate evaluation of the relative importance of these mechanisms can only be attained when more information becomes available on the interplay between cellular and humoral immune mechanisms within the joint.