Of a 49-strain collection of Pseudomonas stutzeri species, 11 isolates were able to degrade naphthalene and 1 isolate was able to use m- and p-toluate as sole carbon and energy sources. Of these 12 strains, 10 shared a highly homologous set of naphthalene catabolic genes, even though they belong to four different genomovars. These genes differed from those present in plasmid NAH7. In only one of these degraders could a plasmid-encoded pathway be demonstrated, and a chromosome-encoded pathway is proposed for the remaining strains. meta cleavage of catechol was only observed in those strains able to metabolize alkyl derivatives of catechol.