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Playas are ephemeral, closed-basin wetlands that are important zones of recharge to the High Plains (or Ogallala) aquifer and critical habitat for birds and other wildlife in the otherwise semiarid, shortgrass prairie and agricultural landscape. The ephemeral nature of playas, low regional recharge rates, and a strong reliance on ground water from the High Plains aquifer has prompted many questions regarding the contribution of recharge from playas to the regional aquifer. Considerable scientific debate has led to more than 175 publications about the potential for water to infiltrate the relatively impermeable playa floors and subsequently recharge the High Plains aquifer. Since the early 1900s, many conceptual models about recharge beneath playas have been proposed. Some early conceptual models indicate that playas are evaporative pans that do not allow recharge beneath playas, whereas other more recent models indicate that playas are effective recharge basins. A variety of data supports various aspects of these competing conceptual models. The competing conceptual models have developed because of the sporadic nature of rainfall to the region, the large number of playas in the region (more than 66,000), a range of physical characteristics in playas, the relatively thick unsaturated zones (often greater than 100 feet) separating most playas from the regional water table, and the inherently uncertain nature of most methods used to estimate recharge. An accurate understanding of recharge rates beneath playas is important from the perspective of groundwater management and the sustainability of rural agricultural economies, particularly in light of the substantial water-level declines in the High Plains aquifer. Other environmental concerns, such as erosion and transport of sediment and contaminants from surrounding land and modification of playas to allow artificial recharge, also have made accurate understanding of recharge an important priority from the perspective of wetland function and habitat health, protecting groundwater quality, and the substantial costs associated with land and water management, conservation, and regulation. To address these questions and concerns, the U.S. Geological Survey, in cooperation with the Playa Lakes Joint Venture, present a review and synthesis of the more than