Hexon is a one of adenovirus capsid proteins (240 hexons per particle). Each hexon capsomere is homotrimer of the hexon protein, a complex protein of >900 residues. 49 human adenovirus serotypes have been discovered, and divided into six subgroup, A to E, based on a variety of observation. They are an important cause of respiratory illness, conjunctivitis, and gastroenteritis and have more recently been recognized as a potential cause of sexually transmitted diseases. Adenovirus vectors, particularly those based on Ad5, have shown great promise for the development of gene therapy protocols and have been used for clinical purpose. More recently, polyclonal antibodies against adenovirus were used for quantifying adenoviral titers.