Proteoglycans and glycosaminoglycans in normal gingival and phenytoin‐induced gingival overgrowth were studied by gel electrophoresis and HPLC methods after extration with guanidinium hydrochloride and subsequent cesium chloride gradient centrifugation. The results showed that normal gingival. The relative collagen content was decreased in the phenytoin lesion. These results are in agreement with our revious stereological study, which reported an accumulation of the non‐collagenous matrix chondroitin sulfates Containing non‐sulfated, 4‐sulfated and 6‐sulfated disaccharide units, dermatan sulfate, hyaluronic acid and presumably also heparan sulfate in both normal gingival. and phenyton‐induced gingival overgrowth. The increased amounts of PGs seen in the PHT lesion were associated with an increase mainly in chondroitinase sensitive glycosaminoglycans of high molecular weight and with a relative increase in iduroinc acid content. This study is consistent with the view that the PHT‐lesion represents a tissue with an altered composition of the conn