A review of the peri-implant sulcus, including the histology of the sulcular epithelium, epithelial attachment, and the gingival connective tissue, is presented. The peri-implant junctional epithelial attachment is mediated by hemidesmosomes, as in the periodontal tissue. There is some controversy on the possible attachment of connective tissue fibers to the implant, but current studies indicate a parallel orientation with no insertion of the peri-implant connective tissue fibers. This difference in connective tissue attachment may affect the peri-implant tissue's susceptibility to disease. Keywords: epithelial attachment, gingival connective tissue, histology, peri-implant sulcus, sulcular epithelium