Normal articular cartilage from subjects of various ages and cartilage from patients with degenerative joint disease were extracted with 4M guanidinium chloride. After dialysis against 8M urea pH 6.8, a 0.2M NaCl fraction was obtained by ion exchange chromatography on DE-52 in 8M urea. This fraction was concentrated, reduced, and analyzed by sodium dodecyl sulfate--polyacrylamide gel electrophoresis (7% gels). Six major noncollagenous protein bands (P1-P6) were found; 2 were identified as the link proteins. The approximate molecular weights of P1-P6 were: 87,000, 64,000, 56,000, 46,000, 41,000, and 27,000. A similar sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern of P1-P6 was found in young baboons, in normal young and aged humans, and in patients with degenerative joint disease. Peaks corresponding to extracted collagen were decreased in older patients and increased in patients with degenerative joint disease, even those of advanced age.