Purpose: Attachment of bacteria to titanium may differ not only between bacterial species but also between strains within a species. The aim of the present in vitro study was to examine differences in bacterial attachment using 4 gram-negative anaerobic species of bacteria that are considered potential periodontal pathogens. Materials and Methods: The attachment of clinical and laboratory strains (n = 23) representing 2 Fusobacterium nucleatum subspecies, Porphyromonas gingivalis, and Prevotella intermedia to smooth, commercially pure titanium was examined using scanning electron microscopy. Results: All bacterial strains were attached to the smooth titanium surface by their outer membrane. F nucleatum cells were poorly attached to the titanium, unlike P gingivalis or P intermedia cells, but only slight differences were observed in the quantity of attached cells between the strains within each bacterial group. Discussion: In favorable conditions, some anaerobes can attach directly to an inert titanium surface. Microbial adhesion and subsequent colonization on the dental implant surface can lead to infecttion of the peri-implant tissue. Conclusion: The results indicated that the avidity of bacterial attachment to a smooth titanium surface varies between species of oral gram-negative anaerobes but not between strains.