The complete nucleotide sequence and the predicted amino acid sequence of the adenovirus type 7 hexon gene were determined. The hydropathy of the hexon proteins from human adenovirus types 2, 3, 4, 5, 7, 12, 16, 40, 41, and 48, bovine adenovirus type 3, murine adenovirus type 1, and avian adenovirus types 1 and 10 was analysed. The presence of purines and pyrimidines in the second position of the codons was correlated to hydrophilicity and hydrophobicity, respectively. Comparison of the hydrophilicity plots of eight hexons showed seven hypervariable regions to be distributed on the surface. A large portion of the hypervariable regions manifests hydrophilicity. The strength of the surface charge accumulated on the hydrophilic and hydrophobic regions correlated to the tissue tropism of the different adenovirus types. Analysis of codon usage for adenovirus hexons showed that among synonymous codons those with cytidine in the third position were preferably used to a great extent. Analysis of the nucleotide and amino acid sequence pair distances and the phylogenetic tree of 14 hexon proteins showed members of subgenera B, D and E to be closely related, especially Ad4 and Ad16, and subgenus A to be closely related to subgenus F.