Vertically　aligned　MgO　nanowires　were　epitaxially　grown　at　600　°C　on　Au-coated　MgO　(001)　substrates　by　metal　organic　chemical　vapor　deposition　using　Mg　(tmhd)　2　precursor.　Discrete　Au　particles　were　embedded　in　the　wires　and　distributed　along　the　central　axis.　Scanning　and　transmission　electron　microscopy　show　that　the　orientation,　diameter,　and　length　of　the　wires　strongly　depend　on　the　processing　conditions　such　as　oxygen　partial　pressure　and　reactive　species　flow　rate　as　well　as　the　starting　Au　thickness.　Diameters　down　to　15-20　nm　were　obtained.　The　growth　can　be　switched　from　vertical　to　horizontal　wires　by　decreasing　the　period　at　which　reactants　are　supplied.　©　2009　American　Institute　of　Physics.