Previous studies to compare the influence of surface characteristics of dental implants on cell behavior have used model systems to simulate the implant surface. In this study, bone cell interactions with smooth titanium, titanium dioxide-blasted, titanium plasma-sprayed, and hydroxyapatite plasmasprayed implants, as manufactured for clinical use, were compared. Implants were exposed to neonatal rat osteoblast cells in suspension for a 20-minute period and, by means of scanning electron microscopy, attached cells were classified according to stage of attachment. Quantitative analysis showed that cells spread most quickly on the titanium plasma-sprayed implants. Fully spread cells on the smooth titanium implants were closely adherent to the surface, while on the titanium dioxide -blasted surface they showed no adaptation to surface irregularities. On the hydroxyapatitecoated implants, cells adhered closely only to smooth areas. To avoid the use of proteolytic enzymes for cell derivation, the authors developed a novel organ culture system in which the implant was contained in a nylon pocket surrounded by bone fragments, permitting cells to migrate onto the implant surface. Cultures were maintained for up to 4 weeks, allowing comparison of cell migration, proliferation, and differentiation on the implant surfaces.