As part of our efforts to develop bovine adenoviruses into a vector system, we sequenced the region predicted to encode the terminal protein precursor of either bovine adenoviruses type 2 and bovine adenoviruses type 3. We examined the regions containing the terminal protein precursors and showed that the bovine adenovirus early region 2B had an identical organization to all adenoviruses so far examined. The bovine adenovirus terminal protein precursors and those of other adenoviruses were also compared in a sequence alignment analysis and several highly conserved structural domains were identified. Finally, we showed how the various terminal protein precursors were related in a sequence pair similarity analysis and concluded that the terminal protein precursors of bovine adenoviruses types 2 and 3 are significantly different from each other at the protein sequence level.