An understanding of bone cell response and extracellular matrix production to a biomaterial is crucial for development of new prosthetic devices. The nature of the cellular-biomaterial surface interface will depend upon a number of factors including substrate properties (surface chemistry, charge, topography) as well as biological cellular concerns (i.e. adsorption of attachment factors to the surface, growth factors). The quality of the matrix and bone-bonding may be influenced by these factors. Recently, a short-term in-vitro cell culture assay has demonstrated the initial attachment and spread of human derived bone cells on metallic (titanium and stainless steel) and polymeric surfaces to be dependent on the adsorption of adhesive attachment factor proteins (fibronectin and vitronectin) to the substratum surface . The morphological appearance of human osteoblasts cultured on titanium and stainless steel with time also demonstrated differences compared to tissue culture plastic . Little data however, is available for the mitogenic and gene expression levels of primary human bone cells cultured on commonly used orthopaedic materials and the response of these cells to growth factors. The present study examined the mitogenic response and steady state mRNA expression levels of primary human bone cells cultured on metallic substrates to provide further insight into the nature of cell-substrate interactions.