Biooxidation of nine retort waters was evaluated in batch culture. Because losses of dissolved organic carbon by volatilization could be extensive, biotreatment was evaluated in screw-capped shale-flasks that contained enough headspace to ensure aerobic conditions. Biological removals of DOC ranged only from 9% to 49% using bacteria subjected to extensive enrichment periods. A simple reverse phase chromatographic fractionation scheme indicated that the majority of refractory DOC for each water resided in the lipophilic fraction; the polar fraction comprise most of the degradable carbon. The LpF organic nitrogen content did not change significantly after biooxidation, and the LpF molar ratio of carbon to nitrogen was similar for each treated water. Molar C:N ratios ranging from 7 to 15, and high UV absorbance's indicated that the malodorous and colored solutes, which are predominantly associated with the bio refractory LpF, primarily comprised aromatic nitrogenous compounds. Extracellular fluid that remained after exhaustive biooxidation of one waste water was used in over 200 enrichment cultures, each of which failed to further remove DOC.