A Sphingomonas species that mineralizes high concentrations of pentachlorophenol (PCP) was isolated from a PCP-contaminated EPA Superfund site. This bacterium, identified as Sphingomonas sp. strain RA2, is able to degrade PCP at concentrations of up to 300 mu g/mL in liquid culture. This organism was tested for its ability to degrade high concentrations of PCP in a soil that did not contain organisms capable of degrading high concentrations of PCP. When inoculated into contaminated soil, Sphingomonas sp. RA2 mineralized PCP at concentrations of 300, 600, 900, and 1200 mu g PCP/g of soil, but was unable to mineralize 1500 mu g PCP/g of soil. Only very minimal loss of PCP was seen in uninoculated soils. The results of this study demonstrate that Sphingomonas sp. RA2 may be a useful organism for remediation of sites contaminated with high concentrations of PCP.