Human parvovirus B19 (B19) is a small nonenveloped icosahedral virus with a single-stranded, linear 5.6 kb DNA genome. The p6 promoter, at map unit 6 of the viral genome, controls the expression of all B19 transcripts. Some previous reports revealed that this promoter is transactivated by NS1 protein. In an attempt to investigate the roles of other small viral proteins in the control of the p6 promoter activity, various truncated promoter/reporter constructs along with these nonstructural protein expression vectors were introduced into Hela cells. The results showed that the putative X protein upregulated the activity of p6 promoter significantly, but that the 11 kDa protein did not. Furthermore, the possible responsive DNA elements for X protein were identified to be located primarily between nt 265 and 343 of the p6 promoter region. In addition, we observed that deletion of the potential ATF/CREB binding sites located in 5' terminal nucleotide influenced the activity of p6 promoter significantly.