The fiber gene sequences of the human adenovirus types 19 and 37 were determined. The predicted polypeptides exposed a high homology. Ad8, Ad19, and Ad37 can cause epidemic keratoconjunctivitis (EKC), whereas Ad9 only infrequently causes acute follicular conjunctivitis. Comparison of the fiber knobs of Ad8, Ad9, Ad19, Ad37, and other previously published fiber sequences revealed that only two amino acid residues were conserved in the fiber knobs of Ad8, Ad19, and Ad37. Since the knob is responsible for interaction with the cell receptor, these two amino acid residues could play an important role in the pathogenicity of EKC causing adenoviruses.