Two- and three-dimensional radiation transport methods have been employed to estimate the nuclear performance of the neutral beam injectors being designed for the Tokamak Fusion Test Reactor. The nuclear heating rates and neutron and gamma-ray energy spectra have been calculated at various locations in a detailed calculational model of the injector using Monte Carlo methods. Calculations have also been carried out using discrete-ordinates methods to obtain estimates of these data in a two-dimensional model of the injector. The two-dimensional calculational procedure was developed as an analytic tool for more cost-efficient scoping and parametric studies of the effects of design changes on the injector performance due to the streaming of 14-MeV neutrons. The nuclear responses and spectra obtained using the two-dimensional calculational model agree with the more definitive data obtained using the three-dimensional model within a factor of ∼5.