A six-year experiment (1998-2003) was conducted at Tal Amara Research Station in the Bekaa Valley of Lebanon to determine water use, yield and water use efficiency in four annual crops with contrasting response to deficit irrigation (DI). Crop evapotranspiration (ET) was measured using drainage and weighing lysimeters. In the plots, ET was measured using a simple soil water balance model. Yield and its components were determined in sampling areas reserved for harvest. Water use efficiency at grain (WUEg) or seed (WUEs) basis was calculated as the ratio of dry yield to crop evapotranspiration (Y/ET), while water use efficiency at biomass-basis (WUEb) was calculated as the ratio of dry biomass to ET (B/ET). For cotton, water use efficiency (WUEl) was calculated as the ratio of dry lint yield to ET. Furthermore, the relationships between yield (Y) and biomass (B) in one hand, and crop evapotranspiration (ET) in the other hand were examined using linear models.