A 17.0-kb SacI fragment, which contains a large region just downstream of the aniline dioxygenase genes (atdA1-A5) of Acinetobacter sp. strain YAA, was cloned from YAA plasmid DNA. We determined the nucleotide sequence of a 10.5-kb segment within the fragment, in which eleven genes were found. Eight of the genes, designated atdSBCDEFGH, were homologous to the meta-cleavage pathway genes dmpQBCDEFGH and xylTEGFJQKI the products of which are involved in the phenol and toluene degradation pathways, respectively. The GS-C content of the atdSBCDEFGH genes ranges from 51.1% to 59.5% and is unusual for Acinetobacter genes (38-47%), indicating that the genes originated from other bacteria. In addition, these values are quite different from those of the upstream atdA1-A5 genes (40.1-47.7%). This result suggests that this aniline degradation gene cluster is a hybrid structure.