Considerable research effort has been directed at preparing root surfaces in a fashion that would promote cell attachment leading to periodontal regeneration; however, no methods have proven to be clinically predictable. Identification of attachment protein(s) associated with the root surface matrix of cementum may prove valuable for developing effective clinical treatments. In this study cementum proteins were extracted from bovine and human teeth by sequential chaotropic extraction using guanidine followed by guanidine/EDTA. The guanidine/EDTA extract, but not guanidine extract, was found to promote attachment of fibroblasts. This attachment activity was inhibitable with synthetic peptide containing the attachment sequence arginine‐glycine‐aspartic acid (RGD). Fractionation of the guanidine/EDTA extract revealed several fractions with attachment activity. Immunoblot analysis demonstrated that two of these fractions contain the bone‐associated RGD containing attachment protein, bone sialoprotein‐II (BSP‐II). In addition, attachment activity was also noted in other fractions that could not be attributed to BSP‐II or fibronectin. These studies indicate that a component of the attachment activity of cementum is likely to be due to BSP‐II and that cementum contains additional, as yet undetermined, attach