Practical tokamak reactors will need to maintain high Ti and nD ~ nT in the core for long durations. These conditions will necessitate low energy transport, low impurity concentrations, and high bootstrap current. Large extrapolations from present experiments are needed to predict performance. A number of approaches are being used for these extrapolations including: 1) dimensionless scaling arguments, 2) empirical scaling, and 3) physics-based simulations of anomalous transport.