The electronic properties of Fe3Si and Fe3Al in the cubic DO3 structure are calculated within the local spin density approximation. There are two types of Fe atomic positions, one with tetrahedral symmetry ([A,C]) and one with cubic ([B]) point symmetry. The magnetic properties of the Fe[B] sublattice are similar to those of bcc iron (same symmetry), and this sublattice moment varies smoothly when the volume is varied. The [A,C] Fe atoms, on the other hand, exhibit magnetic phase transitions behavior when the volume is varied similar, and we refer to this as a metamagnetic behavior. The present calculations show that in Fe3Si and Fe3Al the transitions between various high-spin and low-spin phases are expected near and below the equilibrium volume, and experimental observation of the transitions should therefore be possible by means of high-pressure experiments.