Drought is the main limitation for an adequate agricultural activity in the State of San Luis Potosi, Mexico, where one out of three planted corn or sorghum hectares is lost, approximately 120,000 hectares per year, due to drought. The objective of this study was to estimate the pearl millet forage and grain water efficiency, compared to these of corn and sorghum. Three forage and three grain pearl millet, sorghum and corn genotypes were evaluated in three different climatic locations (high, middle, and lowlands, located at 1520, 1100, and 47 m above sea level) in San Luis Potosi State, Mexico. Trials were conducted during the Spring-Summer season of 2004, and rainfall was 392, 446, and 417 mm in the high, middle and lowland location, respectively. A split plot design was used, using species as whole plot and varieties as split plot, with four replications for forage and four replications for grain. Water efficiency (WE) was estimated dividing grain and forage yield by seasonal rainfall in each location. WE mean for grain pearl millet, sorghum and corn yield was 1.047, 0.860, and 0.569 kg/ha/m3 at the highland location; 0.618, 1.179, and 1.068 kg/ha/m3 at the middle location; and 1.338, 0.921, and 0.831 kg/ha/m3 at the lowland location. WE mean for dry forage pearl millet, sorghum and corn yield was 3.438, 2.951, and 1.258 kg/ha/m3 at the highland location; 2.085, 3.400, and 1.334 kg/ha/m3 at the middle location; and 4.299, 4.451, and 3.047 kg/ha/m3 at the lowland location. It was concluded that under the rainfall conditions of the season, pearl millet crop is an excellent alternative for grain and forage production in the high and lowland locations of the study area, compared to sorghum and corn.