A mass balance approach was used to model long-term PCB transport in the Fox River (Wisconsin) from Lake Winnebago to Green Bay. The objectives of this research were to (1) extend the modeling approach for the Fox River to permit realistic long-term simulations of contaminant transport and fate, (2) forecast long-term PCB export from the Fox River to Green Bay, and (3) develop a rational approach for evaluating sediment remediation alternatives. Field data collected as part of the Green Bay Mass Balance Study during 1988-90 and additional data collected by the Wisconsin Department of Natural Resources and the U.S. Geological Survey during 1992-93 were used to develop the model. A 10-year hindcast was conducted to confirm long-term model predictions. A series of 25-year forecasts were then conducted to explore the potential effects of hydrograph structure, extremely high flows, and sediment remediation on long-term PCB export from the Fox River to Green Bay. PCB export from the Fox River is forecast to decrease, and most (75%) of the PCB reservoir in Fox River sediment is expected to remain in place. However, extremely high flows in future years are forecast to cause significant PCB resuspension and export. Model forecasts suggest that long-term PCB export is only mildly sensitive to changes in hydrograph structure. Sediment remediation is forecast to reduce but not eliminate PCB export.