From a crystallographic point of view, the transition from the L1(2) to DO19 phase is an ordered version of the widely investigated fee to hcp transformation. In the present study, the transformation kinetics of the forward and backward reactions of the L1(2) <-> DO19 transitions in Fe3Ge have been studied and it is shown that a large hysteresis exists between the forward and backward reactions. The detailed microstructural changes that accompany the L1(2) <-> DO19 transition have been characterized and these explain the observed transformation hysteresis.