In order to investigate a possible mechanism of degradation of cartilage matrix in chronic inflammation, superoxide anion (O2-) release from chondrocytes after stimulation with interleukin 1 (IL 1) and interferons (IFNs) has been studied. Both of these cytokines enhanced O2- release in a dose- and time-dependent fashion. Increased of the O2- release by these cytokines inactivated by heat or acid pretreatment was not observed. These results suggest that the cytokines released in the process of local immune reactions can stimulate the chondrocytes to promote generation and release of O2-. Released O2- may be associated with degradation of cartilage matrix by chondrocytes themselves activated in the process of chronic arthritis.