Hosts for Strophitus undulatus (Bivalvia: Unionidae) were identified through laboratory infestations. Strophitus undulatus had a low degree of host specificity, transforming on 15 of 22 species examined, including three non-native species and one anadromous species. Suitable hosts included five cyprinid species, two salmonids, two centrarchids, two percids and Acipenser oxyrhynchus (Atlantic sturgeon), Ameiurus natalis (yellow bullhead), Cottus cognatus (slimy sculpin) and Notophthalmus viridescens viridescens (red-spotted newt). Ten hosts were previously unknown. No metamorphosis was observed in a control treatment without a potential host. Recovery of juveniles occurred 12–41 d after infestation at 13–18 C. Duration of glocidial attachment to the hosts declined with increasing water temperature.