The purpose of the work is to have a nucleotide sequence of some of the regulatory regions of VK virus genomes and compare these to the SV40 genome in order to better understand the gene structure and function of the papovaviruses. A detailed nucleotide sequence analysis has been performed on the segment of the BK virus genome that carries the origin of initiation of DNA replication. Sequences flanking both sides of the origins of replication of BK virus appear to have approximately 70 to 80% sequence homology with SV40 DNA.