In this chapter, we discuss how to model effects that arise in transistors with short channel lengths. Such short-channel transistors have correspondingly thin gate oxides, shallow source/drain junctions, high doping, and small operational supply and threshold voltages. The models are accurate for transistor lengths that range from 1 μm to 0.01 μm (10 nm), where semi-classical approximations of transistor function are still valid. We shall allude to some quantum phenomena as well. We shall begin by first describing the EKV model in a long-channel transistor. The EKV model is an insightful charge-based model that captures subthreshold and above-threshold operation in a simple analytic fashion. It is named after its originators, Enz, Krummenacher, and Vittoz. Then, based on a short-channel model in [2], we shall modify the long-channel EKV model to describe a short-channel effect that is important in above-threshold operation, namely velocity saturation. As the lateral electric field in a transistor increases with increasing drain-to-source voltage, the drift velocity of electrons in short-channel transistors begins to saturate and limit at a maximum velocity vsat; the drift velocity is then no longer related to the lateral electric field via the mobility proportionality constant as it is in long-channel transistors.