The chondrocytes of pure articular cartilage from young pigs display collagenolytic activity when the cartilage is cultivated by an organ culture method in medium containing 5--10 IU retinol/ml. Breakdown of collagen occurs in all regions of the cartilage; in the thicker explants it is greatest and most frequent in those that contain the deepest zone composed of proliferating and hypertrophic chondrocytes; it is also very drastic in thin explants composed mainly of superficial fibro-cartilage.