Calcium, sulfur, and zinc content in normal and arthritic equine cartilage have been studied by synchrotron radiation-induced X-ray emission (SRIXE). Ranging from the superficial to the columnar zone of the normal tissue, calcium and zinc concentrations are increasingly higher, whereas sulfur is at its highest concentration in the transitional zone. In the arthritic tissue, calcium concentration is at its maximum in the transitional zone, whereas zinc and sulfur distributions are relatively homogeneous. Sulfur concentration in arthritic cartilage is reduced to about one-third with respect to that in normal tissue. The possibility that zinc concentration reflects the distribution of the zinc-containing enzyme alkaline phosphatase is presented.