A group of 74 Aeromonas isolates from surface water of three ponds in Bielefeld, Germany was screened for prophage induction after UV irradiation. The phage PhiO18P was induced from the Aeromonas media isolate O18. PhiO18P belongs to the Myoviridae phage family. The complete nucleotide sequence of the double stranded DNA genome of bacteriophage PhiO18P consists of 33,985 bp. The genome has 5' protruding cohesive ends of 16 bases. On the PhiO18P genome 46 open reading frames (orfs) were identified which are organized in the modules integration and regulation, replication, head, packaging, tail and lysis. Additionally the phage DNA includes a methylase gene. Comparison of the genome architecture with those of other bacteriophages revealed significant similarities to the P2 phage family and especially to the prophages of Aeromonas salmonicida and the Vibrio cholerae phage K139.