The diversity of a gene family encoding Actinobacterial aromatic ring oxygenases (AAROs) was detected by the PCR-cloning approach using a newly designed PCR primer set. The distribution of AAROs was investigated in 11 soils representing different land management and vegetation zones and was correlated with several geochemical parameters including pH, organic matter (OM), total Kjeldahl nitrogen (TKN), and nitrogen oxides (NO(x)-N: mostly NO3(-)-N). The distribution of individual clades encoding enzymes with potentially different substrates were correlated with different environmental factors, suggesting differential environmental controls on the distribution of specific enzymes as well as sequence diversity. For example, individual clades associated with phthalate dioxygenases were either strongly negatively correlated with pH, or not correlated with pH but showed strong positive correlation with organic carbon content. A large number of clones clustering in a clade related to PAH oxygenases were positively correlated with pH and nitrogen, but not with organic matter. This analysis may yield insight into the ecological forces driving the distribution of these catabolic genes.