This document focuses on the state of the science for five subspecies of cutthroat trout found largely on public lands in the Rocky Mountain and Intermountain West. These subspecies are restricted to a fragment of their former range, and primarily occupy small, high-elevation streams. Little is known about the three rarest subspecies (Bonneville, Colorado River, and Rio Grande cutthroat trout), and the data on the more abundant subspecies (westslope and Yellowstone cutthroat trout) were obtained from relatively few areas. The historic diversity of life history strategies has been reduced. All subspecies have suffered from introductions of nonnative fishes, habitat degradation and fragmentation, and overfishing. Current management often centers on restrictive angling regulations, barricading streams to prevent invasion by nonnative fishes, and reintroductions into streams with existing barriers.