Ballistic transport in GaAs has been studied using an ensemble Monte Carlo simulation. Duration and spatial extent of ballistic transport for a hot electron distribution can be defined from such studies. Mean displacement of the ensemble increases quadratically with time for a specified interval. This observation provides a phenomenological definition of ensemble ballistic transport. This phenomenological definition is compared with a theoretical definition based on time at which a significant fraction of an ensemble have experienced at least one collision. From these studies, times and distances are given for which a single-particle ballistic equation and a Langevin equation accurately describe ensemble transport in GaAs.