Human teeth extracted because of advanced periodontal disease were obtained. The portions of the roots which had been exposed in periodontal pockets were either untreated or were treated with root planing or citric acid, or root planing followed by citric acid. Human gingival fibroblasts were then added to the roots so treated and were allowed to incubate for 72 h. The ability of cells to attach to and grow onto these roots was assessed by means of gross evaluation of staining intensity and by histologic and scanning electron microscopic observation. The results of multiple experiments in each root-treatment category indicated that only roots which had been planed, whether or not citric acid demineralization was used, promoted cell attachment and growth. In addition, there were no discernible morphologic differences in the cells which were plated onto roots which were root planed only, compared to those which were root planed and citric-acid treated. In both situations too, the cells displayed morphology typical of human gingival fibroblasts in culture.