The direct electron microscopic examination of 15 sutures and 15 staples removed from 10 healed surgical wounds showed, on the intradermal portions, consistent colonization by bacteria growing in adherent biofilms. This clearly demonstrable bacterial colonization of biomaterials within the wound tract had not resulted in infection or perceptible inflammation in any of the wounds. These bacterial cells were of several morphotypes, including gram-positive cocci, and all specimens yielded cultures of the autochthonous (native) skin bacterium, Staphylococcus epidermidis. The bacteria within the wound tracts were enveloped by extracellular material that appeared on scanning electron microscopy to be a condensed amorphous residue and on transmission electron microscopy to be a fibrous extracellular matrix. We suggest that this mode of growth, in which the colonizing bacteria are enveloped in a copious exopolysaccharide glycocalix, protects the bacteria from host defense factors and accounts for their persistence on the suture surfaces until they are removed with the sutures.