With the possible exception of very simple viruses, most viruses appear to encode at least one virus specific endopeptidase. In addition to facilitating the orchestrated fragmentation of polyproteins of RNA viruses, these proteolytic enzymes may also be involved in the suppression of host protein synthesis, the regulation of virus assembly, the egress and subsequent uncoating in another cycle of infection of both RNA and DNA viruses. The endopeptidase encoded by adenoviruses (AVP or adenain) appears to be involved in several of these functions. Most of the literature concerns the protease of human adenovirus type 2, but there are good reasons to believe that the proteases of other adenovirus serotypes will be very similar. For a review see Weber [1,2].