We have examined the ability of a synthetic 15-residue peptide, P-15, related to a biologically active domain of type I collagen, to promote attachment of human dermal fibroblasts to anorganic bovine bone mineral (ABM) phase. The attachment of cells increased with increasing content of P-15 on the surface of ABM particles, as seen by the increased binding of radiolabeled cells, and by light microscopy and scanning electron microscopy. Incorporation of radioactive precursors of DNA and protein synthesis showed that cells on P-15-coated ABM synthesized over twofold the amount of DNA and protein than did cells on uncoated ABM. Fibroblasts attached to ABM in the presence of P-15 formed three-dimensional colonies. Cellular bridges formed between adjacent particles which aggregated in clusters with tissue-like structure. Cultures on ABM.P-15 stained for alkaline phosphatase. These observations suggest that P-15-coated ABM may be a useful matrix for bone repair.