The genus Spongospora belongs to the taxonomic group, plasmodiophorids. There are four known plant-pathogenic, soil-borne, Spongospora species, with S. subterranea as the most important member that infects potato, resulting in powdery scab, root zoosporangia, and root galling. Current Spongospora disease control measures can reduce disease incidence and severity but not eliminate high-inoculum in the soil. Current disease control programs do little for the long-term management of resting spore-inoculum in the soil. However, progress in management of this pathogen has been made over the past years. This chapter reviews information on the genus Spongospora, emphasizing S. subterranea, the potato powdery scab pathogen.