Sulfate-reducing bacterial enrichments were obtained from a shallow anoxic aquifer for their ability to metabolize either o-, m-, or p-cresol. GC/MS and simultaneous adaptation experiments suggested that the anaerobic decomposition of p-cresol proceeds by the initial oxidation of the aryl methyl group to form p-hydroxybenzoic acid. The intermediate was then converted to benzoic acid. Benzoic acid and a hydroxybenzaldehyde were also found in spent culture fluids from an o-cresol-degrading enrichment culture. The result, in addition to others, suggested that o-cresol may also be anaerobically degraded by the oxidation of the methyl substituent. An alternate pathway for anaerobic m-cresol decomposition might exist. Enrichment cultures obtained with either p- or o-cresol degraded both of these substrates but not m-cresol. In contrast a m-cresol enrichment culture did not metabolize the ortho or para isomers. Anaerobic biodegradation in all enrichment cultures was inhibited by molybdate and oxygen, and was dependent on the presence of sulfate as a terminal electron acceptor. (Copyright (c) 1989 Society for Industrial Microbiology.)