The term JIT (Just in Time), when used as a manufacturing control system, has become very confusing over the past few years. Everyone wants to claim they are users of JIT systems and because of this a variety of systems creations, all claiming themselves to be JIT systems, have sprouted up, none of which look anything like what Japan uses. This article attempts to clear up some of this confusion by showing four different variations of JIT and comparing them to the traditional MRP/MRP II environment.