Chicken chondrocytes isolated from 11-day-old chicken vertebrate cartilage were transformed by Rous sarcoma virus ts LA24 of the Prague strain as well as by the wild-type Prague strain of Rous sarcoma virus. The morphology of chondrocytes transformed by Rous sarcoma virus ts LA 24 was dependent on the temperature, and the change was reversible. A similar but irreversible change in morphology was observed with chondrocytes transformed by wild-type virus. Hyaluronic acid production and deoxyglucose transport were markedly increased in the transformed chondrocytes. A marked increase of labeled acetate incorporation was observed with the transformed chondrocytes. In contrast to the normal chondrocytes, the labeled hyaluronic acid synthesized by the transformed chondrocytes was mostly released into the culture medium.