Swinepox virus (SPV), the prototype member of the Suipoxvirus genus, is uncharacterized at the molecular level. We have analyzed the DNA of SPV and demonstrate that the genome is 175 kb in size and like the more commonly studied Orthopoxvirus, Avipoxvirus, and Leporipoxvirus genera, is terminally cross-linked and contains inverted terminal repetitions (ITRs). In addition, the ITRs are unstable, probably due to the presence of a variable number of direct repeats of approximately 70 bp in length. Restriction enzyme cleavage maps for the enzymes HindIII, AvaI, HaeII, KpnI, BglI, SalI, and XhoI are also presented.