Epitaxial growth of cuprous oxide (Cu2O) has been achieved on (1 0 0) and (1 1 0) orientations of MgO by plasma-assisted molecular beam epitaxy. Growth was investigated using a pure oxygen plasma as well as a 90%Ar/10%O-2 plasma. Cu2O films grown using pure oxygen on MgO (1 0 0) have a limited growth window and typically exhibit multiple phases and orientations. Films grown on MgO (1 1 0) using pure oxygen are phase stable and predominantly (1 1 0) oriented, with some (2 0 0) orientation present. Films grown using an Ar/O-2 plasma on MgO (1 0 0) have improved phase stability and a single (1 1 0) orientation. Growth on MgO (1 1 0) using an Ar/O-2 plasma yields highly reproducible (1 1 0) oriented single phase Cu2O films with a much wider growth window, suggesting that this substrate orientation is preferable for Cu2O phase stability. (C) 2014 Elsevier B.V. All rights reserved.