Four DNA sequences (ARSs) that are able to initiate DNA replication in yeast were isolated from mitochondrial DNA of Phytophthora nicotianae and localized on its physical map. Nuclear sequences from P. nicotianae were shown to initiate DNA replication in yeast only very rarely. Minimal regions necessary for replication catalysed by mitochondrial ARSs were delimited by DNase I digestion and sequenced. Transformation efficiencies were estimated for full-length ARS-carrying DNA fragments. Segregation rates and mitotic stabilities in S. cerevisiae were determined for the two shortest subclones of each of the three delimited ARSs. Replication properties of all three ARSs were similar to those of a yeast nuclear ARS sequence. Sequence analysis revealed the presence of many copies of the motif (T/G)ATATTTT, which is related to the ARS core consensus sequences, in all three elements. In two of them, four copies of the motif and its reverse complements were arranged in palindromes. In addition, whole ARS core sequences and long segments consisting exclusively of A and T nucleotides were found in all ARS analysed. These features indicate that an HMG-like (high mobility group) DNA-binding protein similar to ABF2 from yeast may participate in DNA packaging also in non-fungal mitochondrial lineages.