The purpose of this study was to investigate the changes in concentration of glycosaminoglycans (CAGs) and to investigate the incorporation of 3H-glucosamine into GAGs in vitro in the epithelium and sub-epithelium connective tissue separated from the gingiva during a period of experimental periodontitis. Periodontitis was induced by placement of a silk ligature below the gingival margin in dog molars. The GAGs extracted from gingival samples obtained 0, 7, 21, 60 and 90 days before and after the ligature placement were separated by cellulose acetate membrane electrophoresis for both qualitative and quantitative analysis. Hyaluronic acid content of the epithelium was decreased significantly at the acute phase of inflammation. In the connective tissue, the amounts of dermatan sulfate and hyaluronic acid were higher, but chondroitin sulfate and heparan sulfate levels lower than in the control. The incorporation of 3H-glucosamine into GAGs in the epithelium was greater than that in connective tissue at the acute phase. The greatest incorporation of 3H-glucosamine was found in chondroitin sulfate at the acute phase, and did not return to the basal level at the chronic phase. These findings suggest that the biochemical response of GAGs in the epithelium to inflammation might be different from that in connective tissue.