Abstract
U. maydis chromosomal DNA sequences which promote the autonomous replication of plasmid YIp5 in S. cerevisiae YNN27 have been isolated and three of them characterised in some detail. Their properties are idential to yeast ars sequences in that plasmids containing them are maintained extrachromosomally as circular double-stranded DNA molecules, are mitotically unstable in yeast transformants and transform yeast at high frequencies. There is no sequence homology between the three U. maydis sequences and they are not reiterated in the U. maydis genome.