With the objective of investigating differential tolerance of maize inbred lines to aluminum (Al) and its interaction with high proton activity, in nutritive solution, two experiments were carried out in green houses. In the first experiment, six maize inbred lines from EMBRAPA´s breeding program were evaluated in four different Al concentrations (0, 55, 111 and 222 μM) and in the second experiment, the same lines were evaluated in nutritive solution with four different pH values (3.8, 4.2, 4.6 and 5.0). During transplant and five days of treatment, seminal root length was measured for all treatments. From the inbred lines evaluated, four were Al tolerant (Cateto Al 237, SLP 181, L 1154, L3) and two were sensitive (L 53 and L 36). There was no defined correlation between Al tolerance and tolerance to high proton activity in nutritive solution. The tolerance characteristic was better evaluated in the concentration of 222 μM of Al, suggesting that this concentration will be utilized in future studies of genotype selection. It was also verified that the pH value of 4.2 was more adequate for the present study conditions