Abstract: Hepadnaviridae is a DNA virus family including human hepatitis B virus (HBV), woodchuck hepatitis B virus (WHV), and duck hepatitis B virus (DHBV). Despite differences in genomic structures, DHBV is similar to HBV in replication strategy, infection outcome, and sensitivity to antiviral treatment. It is a safe animal model for HBV and has facilitated understanding of HBV. In this study, newly isolated DHBVs from California and Indiana were cloned by PCR and their nucleotide sequences (3021 bp) determined. Both isolates contained three overlapping open reading frames encoding surface (Pre-S/S), core structure (Pre-C/C), and polymerase (P) proteins. Phylogenetic analysis based on nucleotide sequences showed they were closely related to other USA isolates ($99% identity) and were placed in AWestern country@ DHBV group. When the amino acid sequences of surface protein (S) were compared, a similar genetic tree with closer distances was produced. More diversity occurred between mammalian and avian hepadnaviruses. Pre-S and P proteins varied most among viral proteins. The Pre-C/C proteins were highly conserved with divergence less than 3.8%. Variations in P protein were located in its non-functional overlapping part, called spacer domain, within pre-S proteins. Data provided knowledge of the molecular and phenotypic characteristics of avihepadnaviridae.