Basic research on osteoarthritis has been carried out mainly from the his tological and biochemical aspects of the degenerating chondrocytes, collagen fibers, and matrix proteoglycans. Undue mechanical stress has been shown to be the principal factor in the initiation of osteoarthritis. Although the exact process by which mechanical stress leads to the total destruction of cartilage tissue remains unclear, several new research methods have enabled us to gain a deeper understanding of the process of degeneration. In October 1997, we organized an international symposium titled "Ad vances in Osteoarthritis" in Kobe, with the main topics being updated re search, diagnosis, and treatment of osteoarthritis. The proceedings of the symposium are presented here in five sections: (1) Mechanical stress and reactions of chondrocytes, such as intracellular ion changes, changes in the cytoskeleton, intracellular messenger systems, release of gas mediators, and changes in electromechanical properties of cartilage; (2) Functional diagnosis of osteoarthritis by MR imaging, and using calpain and collagenase III as new cartilage markers; (3) Treatment with a promising simple washout technique and IL-1RA and MMP antagonists; (4) Cartilage repair by new grafting tech niques; and (5) Problems following total joint replacement. We sincerely hope that the advanced knowledge provided in this volume of proceedings will be valuable to our readers.