Recent research has suggested that there is significant predictability of hydrologic extremes, on timescales from synoptic to interannual in a region encompassing the central Asian republics and a southern tier of countries ranging from Iraq to northwestern India (approximately 40¿-80¿E, 25¿-55¿N). Water scarcity, irrigation demand, and a combination of other factors make the population of this semiarid region particularly vulnerable to hydrologic variability, and predictions of this variability would be of great societal benefit. The investigation of the hydroclimatic variability of the region poses a number of scientific and practical challenges due to data scarcity, high mountains, complex land surface characteristics, and key physical processes that remain poorly understood. To review progress in understanding and predicting hydrologic variability, survey available data, consider societal applications, and identify key challenges, a U.S. National Science Foundation (NSF) workshop, Hydrology of Central-Southwest Asia, recently was held in San Diego, California.