The effects of low aluminum (Al) activity in nutrient solution on the concentrations of organic acids in two cultivars of maize (Zea mays L.), HS7777 Al-sensitive and C525-M Al-tolerant, were studied. Aluminum stress increased total organic acid concentration in the roots and in the shoots for both cultivars. The relative increase of t-aconitic, citric, formic, malic, and quinic acids was higher in the roots than in the shoots for both cultivars. The concentrations of c-aconitic, isocitric, malonic, oxalic, and succinic organic acids were reduced by Al stress, principally for C525-M. There were no consistent differences in organic acid concentrations between the cultivars to discriminate Al tolerance. The Al tolerance for C525-M may be justified by lower Al concentrations in the root tips where cellular division takes place and/or by higher excretion of organic acids from roots to the rhizosphere for detoxification of Al by chelation.