Cementum is a specialized mineralized tissue providing for the attachment of perio‐dontal fibers to the root surface of a tooth. In periodontal disease this connective tissue attachment to the cemental surface is lost. The ability of bacteria to adhere to the root surface, an intial event in the disease process, may be influenced by the organic matrix of cementum. Therefore, an in vitro assay of cell attachment was modified to study bacterial adherence to protein extracts of cementum. Petri dishes coated with the extracts were pre‐incubated in culture media and then bacteria were added. Using this assay, Capnocytophaga‐like species, a gram negative bacterium implicated in periodontal disease, attached preferentially to dishes coated with cemental extracts when compared with Type I collagen or uncoated dishes. This assay system should prove beneficial for studying the attachment of various microorganisms to protein extracts of both normal and diseased cementum. as well as providing insight into the unique attachment properties of cementum.