Chondrocytes obtained from rat articular cartilage and Swarm rat chondrosarcoma were maintained in culture. Human interleukin-1 (IL-1) was added at confluency, and three days later the spent media was evaluated for proteoglycan- and collagen-degrading enzymes. Unlike chondrocytes from articular cartilage from several species, chondrocytes from Swarm rat chondrosarcoma did not respond to IL-1 stimulation. This lack of sensitivity to IL-1 may be a useful biochemical marker to classify various types of chondrosarcomas. However, it appears that the use of chondrosarcoma chondrocyte cultures are not useful as a source for metalloproteinases.