Cloning and sequencing of the circular, single-stranded DNA of one isolate of psittacine beak and feather disease virus (BFDV) demonstrate a genome composed of a circular molecule of 1993 nucleotide bases. An analysis of the assembled replicative form demonstrated seven open reading frames (ORFs) (three in the virion strand and four in the complementary strand), potentially encoding seven viral proteins of >8.7 kDa. High amino acid sequence similarity was demonstrated between a potential 33.3-kDa protein product of ORF1 of BFDV and the replicase-associated protein of porcine circovirus (PCV), subterranean clover stunt virus, and faba bean necrotic yellows virus. However, significant similarity in nucleotide or amino acid sequences was not present between BFDV and chicken anaemia virus. A potential stem-loop structure similar to that found in PCV and plant circoviruses was present in the putative encapsidated strand of the BFDV genome. At the top of this structure, a nonanucleotide motif (TAGTATTAC) similar to that of PCV, plant circoviruses, and geminiviruses also was recognised. Comparison of the deduced amino acid sequences of ORF2 of BFDV and PCV demonstrated 29.1% identity, and in both viruses, ORF2 is located on the complementary strand, beginning close to or within the hairpin stem. Our findings provide further evidence of a close relationship among BFDV, PCV, and plant circoviruses but not chicken anaemia virus.