The great challenge of the agricultural sector in countries located in arid and semiarid regions faced with severe water scarcity is to produce more food from less water. This may be achieved by increasing the crop water productivity (WP). Based on experiments conducted in different regions of Iran, it was found that the range of wheat WP was greater than that reported earlier by the FAO. The maize WP was high in the northwestern regions of Iran and less in the southwest. The wide ranges of WP (0.5-1.8 kg m À3 for wheat and 0.3-2.3 kg m À3 for maize) indicate tremendous opportunities for increasing agricultural production with less water. The variability of crop WP can be ascribed to climate, cropping calendar, soil characteristics, and irrigation water management. Wheat and maize WP of 1.5 and 1.7 kg m À3 were recommended as an optimum level to be considered in the cropping system of potential regions. Irrigation water applied for an optimum level of wheat and maize WP was about 2650 and 5900 m 3 ha À1 , respectively. The maximum wheat WP occurred under deficit irrigation, while for maize it was measured under full irrigation. Regions with higher annual rainfall and high silt content in soil were more productive under deficit irrigation management. Copyright # 2008 John Wiley & Sons, Ltd.key words: crop water productivity; crop water production function; wheat; maize; deficit irrigation