Abstract: The objective of this research was to evaluate the effect of water stress on stomatal closure of 2 maize cultivars. Water stress was generated by additions of Polyetylene glycol 6000 to the root medium. Water potentials were: zero (control), - 0.15 (PEG 10%), - 0.49 (PEG 20%), -1.03 (PEG 30%) and -1.76 (PEG 40%) MPa. After 24 h treatment, the leaves stomatal of 2 maize (Zea mays L.) cultivars -704 and 301- were photographed in various concentrations of PEG 6000. Stomatal closure was particularly apparent at low water potentials. In low water stress, stomata were open and in moderate water stress, leaves started to close their stomata. Maize leaves closed their stomata after 24 h PEG treatments and stomatal closure in 704 var. was higher than 301 var. Therefore, the stomata of 704 var. were sensitive to water stress than 301 var.