The aim of this study was to determine the effects ol intra-articular Hyalovet ® 20 (Trans Bussan S A . Geneve, Suisse, hyaluronic acid) on experimental osteoarthntis in dogs. The anterior cruciate ligament of the right knee was cut by blind section in 6 adult dogs. Synovial fluids and sera were obtained under sterile condition before and after operation by needle aspiration. They were also collected after Hyalovet > 20 Ireatment within 15th days. The me! alio pro tein ases (MMP) activity was measured in synovial fluids by gelatine zymography. Glycosammoglycans and keratan sulphate has been measured in sera and synovial fluids. Hyaluronic acid provided good clinical benefits and an acceptable safely profile is current clinical practice.