The entire genome of the hepatitis D virus has been shown to be a circular single-stranded RNA of 1679 bases. Several open reading frames in both the genomic and complementary strands indicate possible protein products. The products encoded in one open reading frame. ORF5, are identified as vital polypeptides p24.sup..delta. and p27.sup..delta., of which the nuclear .delta. antigens in HDV infected liver is comprised. These products, as well as others encoded in ORFs 1, 2, 6, and 7 are produced in recombinant expression systems. The ORF5 products, in particular, are useful for HDV diagnosis and vaccines.