The aerobic polyaromatic hydrocarbon (PAH) degrading microbial communities of two petroleum-impacted Spartina-dominated salt marshes in the New York/New Jersey Harbor were examined using a combination of microbiological, molecular and chemical techniques. Microbial isolation studies resulted in the identification of 48 aromatic hydrocarbon-degrading bacterial strains from both vegetated and non-vegetated marsh sediments. The majority of the isolates were from the genera Paenibacillus and Pseudomonas. Radiotracer studies using (14)C-phenanthrene and (14)C-pyrene were used to measure the PAH-mineralization activity in salt marsh sediments. The results suggested a trend towards increased PAH mineralization in vegetated sediments relative to non-vegetated sediments. This trend was supported by the enumeration of PAH-degrading bacteria in non-vegetated and vegetated sediment using a Most Probable Numbers (MPN) technique, which demonstrated that PAH-degrading bacteria existed in non-vegetated and vegetated sediments at levels ranging from 10(2 )to 10(5 )cells/g sediment respectively. No difference between microbial communities present in vegetated versus non-vegetated sediments was found using terminal restriction fragment length polymorphism (of the 16S rRNA gene) or phospholipid fatty acid analysis. These studies provide information on the specific members and activity of the PAH-degrading aerobic bacterial communities present in Spartina-dominated salt marshes in the New York/New Jersey Harbor estuary.