This article describes the nucleotide sequence of a porcine circovirus (PCV) which possesses a high degree of association with postweaning multisystemic wasting syndrome (PMWS), a newly described disease of young pigs. The DNA sequence of this PMWS-associated PCV (pmws PCV) has 68% homology with that of a previously published nonpathogenic strain of PCV. The strains appear to be closely related yet distinct from one another.