Interactions between Porphyromonas gingivalis and gingival epithelial cells were investigated. Gingival epithelial cells were cultured from surgically removed gingival tissue. Electron microscopy demonstrated adherence of P. gingivalis to the cell membranes and microvilli followed by internalization of the bacteria into the epithelial cell cytoplasm. Saliva from healthy and periodontally diseased patients inhibited P. gingivalis association with the epithelial cells. Attachment to and penetration of gingival epithelial cells by P. gingivalis may be important virulence factors in periodontal disease. Salivary molecules may play a role in modulating these interactions.