Abstract : Osteoarthritis is the most frequent articular disease but until now no treatment exists. It is characterized by a destruction of cartilage and its components as proteoglycans. Major cartilage's proteoglycans are chondroitin sulfate, which are linear and heterogeneous polysaccharides composed of disaccharidic repeating units constituted of a D-glucuronic acid and an N-acetyl-D-galactosamine. In order to study biosynthesis of those compounds and so to better understand working mechanism of the implicated enzymes, chemical syntheses of biotinylated chondroitin and chondroitin sulfate oligomers have been achieved. Thanks to an efficient hydrolysis of a starting chondroitin sulfate polymer, key building blocks were quickly obtained. An elongation strategy using them has been then applied to give a first family of seven non sulfated oligosaccharides (from disaccharide to octasaccharide). Two new families of chondroitin sulfate A and C oligosaccharides, with homogeneous sulfation have been prepared from a common precursor by divergent strategy. For the first time, two chondroitin sulfate A oligosaccharides with an heterogeneous sulfation have been synthetized. This work has led to thirteen final biotinylated oligosaccharides.