Actinemys marmorata (Family Emydidae) occurs in the Pacific States of North America from Baja California Norte north through Washington and, possibly, into southernmost British Columbia, Canada. Recent genetic studies indicate the presence of four groups or clades within the species, although historically there were two recognized subspecies. The species appears to be declining in abundance in the northernmost and southernmost portion of its range, but not in the core of its range from central California to southern Oregon. The primary threats are loss and alteration of both aquatic and terrestrial habitats. These losses fragment remaining populations and, perhaps, magnify the effects of introduced species through predation, competition, and epidemic disease(s). Historically, A. marmorata were collected for the food and pet trades. Most states now protect the species and, in Washington, it is listed as Endangered. Research is ongoing on many aspects of the species' ecology, but not all of the studies are published. Greater effort is needed to protect and manage aquatic habitats as well as nesting and overwintering sites in adjacent uplands.