Using a Vlasov code for simulating fully nonlinear behavior of a plasma driven by an applied potential drop, it is shown that fast solitary potential pulses in the form of electron holes are a common feature of the high potential side of a strong double layer. Temporal and spatial features of the electron holes seen in the simulations are compared against the measurements from FAST. The evolution of the electron beam accelerated by a double layer and that of the plasma on its high potential side generate the suitable conditions for nearly continuously creating fast moving electron holes. ¿ 2000 American Geophysical Union