EPA is publishing final revisions to the polychlorinated biphenyl (PCB) ambient water quality criteria for human health and wildlife for the final Water Quality Guidance for the Great Lakes System that was published in March 1995 (the 1995 Guidance). The final revisions are limited to the method for calculating a composite baseline bioaccumulation factor (BAF) for PCBs and the method for calculating a composite octanol-water partition coefficient (K<INF>ow) for PCBs. After reviewing all public comments, EPA concluded that the approach it proposed in October 1996 for calculating a composite baseline BAF, using the second alternative proposed for calculating a composite K<INF>ow, for PCBs would be preferable to the approach used in the 1995 Guidance because it would more appropriately relate the concentrations of the PCB congeners in tissue to the concentrations of the PCB congeners in water. Consequently, EPA is today revising the human health cancer criterion for PCBs from 3.9E-6 ug/L to 6.7E-6 ug/L, and the wildlife criterion for PCBs from 7.4E-5 ug/L to 1.2E-4 ug/L. EPA believes that these revisions more accurately represent the numerical limits necessary to protect human health and wildlife in the Great Lakes System.