The Physarum polycephalum actin promoter, PardC, can drive transient expression of heterologous genes in Physarum amoebae. The hph gene, encoding hygromycin (Hy) phosphotransferase, can confer resistance to Hy on a broad spectrum of organisms. When PardC is translationally fused to hph and transformed into yeasts on high-copy-number vectors, the yeasts become Hy resistant (Hy[superscript: R]), showing that PardC-hph is a functional, selectable genetic element. To establish a stable transformation system for Physarum, we electroporated plasmids bearing PardC-hph into Physarum amoebae and then selected for Hy[superscript: R] transformants. We show that Hy[superscript: R] amoebae arise upon the stable integration of PardC-hph into the nuclear genome in single copy. These results establish a transformation system that can be used to add plasmidborne genetic information to Physarum. ; 103354