Root cortical aerenchyma (RCA) is commonly associated with hypoxia tolerance. Aerenchyma is also induced by nitrogen, phosphorus or sulfur deprivation. Aerenchyma may have adaptive value under nutrient stress by reducing the metabolic costs of soil exploration by converting respiring cortical cells to air space. We hypothesize that by reducing the metabolic cost of soil exploration, RCA may also have adaptive value under drought stress, and that genotypes able to create more RCA will be able to sustain a more extensive root system, capable of acquiring more water than genotypes with less RCA formation. To test this hypothesis we evaluated the drought tolerance of 27 maize genotypes (recombinant inbred lines from two crosses) with contrasting RCA formation. Plants were grown for 4 weeks in 15.24 cm wide, 1.5 m tall PVC cylinders of fertile soil under adequate or limiting irrigation. Transpiration, photosynthesis, biomass production, root depth, root proliferation and root respiration were recorded and associated with the actual presence of aerenchyma in nodal roots. RCA varied substantially among genotypes. Genotypes with greater RCA under drought had longer nodal roots, reduced root respiration, increased shoot biomass, and increased stomatal conductance. Our results are consistent with the hypothesis that RCA is a useful adaptation to drought by reducing the metabolic cost of soil exploration.