In comparison to the vegetation of most of temperate North America, the southwestern deserts contain highly unusual plants adapted in form and function to the extremes of arid environments. So striking are some of these plants that three national monuments-Saguaro, Organ Pipe Cactus, and Joshua Tree-are named for them. In each case, it is a single species that gives unique character to the desert landscape within the monument. Of all the remarkable plants of the desert Southwest, the giant cactus, or saguaro (Carnegiea gigantea), stands out in the minds of many Americans as an icon representing the novelty and grandeur of the desert realm. Saguaro National Monument (SAGU) was established in 1933 on the east side of Tucson, Arizona, to protect what was then one of the most awe-inspiring stands of saguaros to be found anywhere in the Sonoran Desert. Yet today, little more than a half century later, the giant, manybranched saguaros have all but disappeared from the original "cactus forest" of the 1930s (Fig. 1). Since the primary mission of National Park Service (NPS) at SAGU is to protect the distinctive cactus species for which the monument was named, the saguaro has understandably been the subject of considerable concern and research at SAGU since the late 1930s. The purpose of this report is to (1) trace the development of various research and monitoring efforts involving the saguaro at SAGU, (2) evaluate the rationale for these investigations, and (3) examine some of the impacts of these research efforts on management decisions and public perceptions regarding the ecological status of this extraordinary plant.