Accurate modeling of MODFETs and of certain novel structures recently proposed requires that a number of physical phenomena occurring in these devices be considered. Among these, some electron dynamic properties of the two-dimensional gas, the influence of deep levels of the doped AlGaAs layers, and the influence of the source parasitic access impedance are reviewed. The presently available models can roughly be sorted into three classes: the particle or Monte Carlo models, the two-dimensional solving methods of semiconductor equations, and the simpler one-dimensional or analytical models. After a brief review of the physical bases on which the models rely, their main capabilities and ranges of applicability are discussed. Some conclusions are drawn as to the effort which must be developed in the near future to improve MODFET modeling. It is recommended that simulations of devices such as SISFETs, multichannel structures, and pseudomorphic AlGaAs/InGaAs transistors be undertaken. >