The complete nucleotide sequence of the genome of porcine adenovirus type 3 (PAV-3) is provided. Methods for construction of infectious PAV genomes by homologous recombination in procaryotic cells are provided. Recombinant PAV viruses are obtained by transfection of mammalian cells with recombinant PAV genomes. The PAV-3 genome can be used as a vector for the expression of heterologous nucleotide sequences, for example, for the preparation and administration of subunit vaccines to swine or other mammals. In addition, PAV-3 vectors can be used for gene therapy and expression of heterologous polypeptides. PAV-3 genome sequences can also be used for diagnostic purposes, to detect the presence of PAV-3 DNA in a subject or biological sample.