Studies in adults suggest a possible association between pulmonary nosocomial infection and bacterial adherence to endotracheal tubes (ETT). Some strains of coagulase-negative Staphylococcus produce a mucoid extracellular material known as slime or glycocalyx that helps bacteria adhere to the surface of biomaterials. We examined by scanning and transmission electron microscope the surface of 29 polyvinyl ETT removed from neonatal patients, and ten unused ETT. Multiple surface irregularities were found in the unused tubes. These irregularities were most prominent in the tip and around the side hole. Amorphous material containing slime-producing bacteria was found on 29 ETT removed from patients. Tubes in place for longer times had greater areas of surface covered; the amorphous material was more concentrated in the areas where surface irregularities were most prominent. No clinical correlation with pulmonary noscomial infection was established.