A simple and inexpensive microcosm approach was used to determine the biodegradability of phenanthrene, anthracene, and associated metabolites 1-hydroxy-2-naphthoic acid and 2,3-dihydroxy naphthalene in creosote contaminated soil. Biodegradation was assessed indirectly by measuring oxygen utilization within soil microcosms receiving additions of the test compounds, relative to appropriate controls. Rates of oxygen consumption in microcosms receiving phenanthrene and anthracene were greater than, or equal to rates associated with the addition of associated metabolites. No significant lag periods were observed for any test compound. The extent of biodegradation of each test compound was estimated using reaction stoichiometries generated from thermodynamic principles governing microbial metabolism. Direct oxygen measurements coupled with reaction stoichiometry provides a method for evaluating the biodegradability of target compounds and is consistent with the strategy of the National Research Council for providing evidence supporting bioremediation at hazardous waste contaminated sites.