Osteointegrated titanium dental implants are widely used biomaterials that have to integrate within the alveolar bone and interact with periodontal soft tissues. In this study, we investigated the immunocytochemical expression of the extra-cellular matrix (ECM) protein fibronectin (FN) and type I collagen (Coll I) in Flow 2002 fibroblast cultures spread on grade III-titanium samples with five different surface topographies and we correlated the immunocytochemical data to the adhesion capability of these cells to the above-mentioned substrates. Five different surfaces of grade III-titanium implants were at first characterized both by scanning electron microscopy (SEM) and by laser profilometry for surface roughness evaluation. After being spread on the biomaterial surfaces, the fibroblasts were left to proliferate for 72 hr and subsequently the cells underwent immunocytochemical procedures for detecting both FN and Coll I. The fibroblasts appeared more adherent to smoother titanium surfaces than to rougher ones; however, the highest cell density was detected on the roughest surface, even if it was unrelated to the highest FN expression. In the other biomaterial surfaces examined, as well as in controls, immunocytochemical FN expression correlated effectively to cell density on the examined substratum, whereas no determinant information was available regarding Coll I. It is reasonable to assume that surface roughness could be a relevant parameter influencing fibroblast adhesion to substrata; however, the evaluation of the cell density only is insufficient, and should be supported by the immunocytochemical FN expression, which could be confirmed as a useful tool in determining implant material biocompatibility. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 169-76).