Tissues from sixty-nine cartilage tumors in sixty-six individuals were obtained at the time of operation and each lesion was graded as benign (seventeen) or as a low-grade (thirty-three) or high-grade (nineteen) chondrosarcoma according to histological and roentgenographic criteria. The material obtained was analyzed by biochemical techniques for its content of water, ash, DNA, total protein (composed of collagen and so-called excess protein), and carbohydrate. In addition, proteoglycan subunit was isolated and the chain lengths of chrondroitin sulphate and keratan sulphate were determined. Analysis of the data showed that for the most part the tumors differed only quantitatively from articular cartilage controls, with the principal variations noted in water, ash, protein, and collagen content. Sugar concentrations were highly variable, but analysis of the proteoglycan subunit showed a distribution of glycosaminoglycans characteristic of immature articular cartilage. Marked shortening of the keratan sulphate chains was noted without significant alteration in the chain lengths of chondroitin sulphate, The wide variations in pattern suggest that the cartilage tumors are not biochemically homogeneous and therefore probably do not represent a single group of genetic errors.