The interactions between carriers and fields in semiconductors at low frequencies (<100 GHz) can be adequately described by numerical solution of the Boltzmann transport equation coupled with Poisson’s equation. As the frequency approaches the THz regime, the quasi-static approximation fails and full-wave dynamics must be considered. Here, we review recent advances in global modeling techniques—numerical techniques that couple carrier dynamics with full wave dynamics. We focus on the coupling between the stochastic ensemble Monte Carlo (EMC) simulation of carrier transport and the finite-difference time-domain (FDTD) solution to Maxwell’s curl equations. We discuss the stability and accuracy requirements for different types of high-frequency excitation (wave illumination vs. ac bias), and present simulation results for the THz-regime conductivity of doped bulk silicon, ultrafast carrier dynamics and radiation patterns in GaAs filaments, and the ac response of GaAs MESFETs.