The presence and distribution of intraepithelial antigen-presenting cells was studied in the keratinized mucosa around healthy osseointegrated implants and teeth. Vimentin, cytokeratins, HLA-Dr, CD18, ICAM-I and CDla-positive cells were assessed by a 3-stage ABC immunoperoxidase system in serial sections from clinically characterized sites. A total of 11 biopsies (7 adjacent to osseointegrated dental implants and 4 adjacent to teeth in healthy volunteers) were qualitatively and quantitatively analyzed. All biopsies displayed the presence of a small inflammatory infiltrate subjacent to themost coronal portion of the junctional epithelium. Intraepithelial antigen-presenting cell markers were present both around implants and teeth. The observations were consistent with the presence of functional local major histocompatibility complex Class II restricted antigen presentation. Quantitative differences were observed by analysis of variance in terms of different locations within the same section (i.e. junctional epithelium vs oral epithelium) and in terms of the source of the biopsy (i.e. implants vs teeth). The significance, if any, of the observed quantitative difference is discussed in terms of different maturity of the local immune response and possible environmental differences. It is concluded that clinically healthy keratinized mucosa around osseointegrated dental implants shares functional similarities with normal gingiva in terms ofantigen presentation. These results further contribute to the characterization of a functional local immune response that represents the basis for long-term clinical success of osseointegrated dental implants.