This study examined the potential to enhance polychlorinated biphenyl (PCB) mineralization in soils by augmenting the chlorobenzoate-degrading capacity of the indigenous microflora. Degradation and mineralization of [14C]Aroclor 1242 was monitored in soils amended with biphenyl and inoculated with bacteria that either cometabolized PCBs, grew on chlorobenzoates or grew on chlorobiphenyls. Mixed inocula, containing both PCB-cometabolizers and chlorobenzoate degraders, were also examined. Mineralization of PCBs was consistently greatest, up to 25.5%, in soils inoculated with chlorobenzoate-degraders alone. In contrast, mineralization was significantly lower in soils inoculated with a PCB cometabolizer alone (10.7%), chlorobiphenyl-mineralizers (8.7 and 14.9%), mixed inocula (11.4 and 18.0%), or non-inoculated (3.1%). Overall PCB degradation, as indicated by recoveries of [14C]PCBs and total PCBs, followed trends similar to that observed with the mineralization data, with the greatest degradation occurring in soils inoculated with the chlorobenzoate-degraders strains JB2 and P111 alone. These results supported the hypothesis that separation of the PCB-cometabolizer and chlorobenzoate-degrader populations in soils may limit PCB mineralization as well as PCB transformations in general. While the mechanism by which the introduction chlorobenzoate-degraders exerted these effects was not elucidated, possibilities included eliminating accumulations of chlorobenzoates, which are precursors of of potential inhibitors (e.g., chlorocatechols), or by providing a large pool from which chlorobenzoate-degrading genes could be exported and biphenyl genes imported, resulting in a hybrid population more active in PCB degradation.