We have determined the complete nucleotide sequence of the DNA of the immunosuppressive variant of the parvovirus minute virus of mice (MVMi) and compared it to the published sequence (12) of the fibroblast-specific strain (MVMp). We have found 175 differences between the two viruses, most of which affect single nucleotides. Despite these differences, the genomic organization of MVMp and MVMi is identical. There are 29 amino-acid changes between the putative viral gene products of MVMi and MVMp, 16 of which are conservative. We discuss the possibility that the differential tissue-specificity of the two variants is linked to differences within the non-transcribed region near the 5' end of the viral genomes.