The aim of this research was to detect the water stress effects on germination and vigor of flat and round corn seeds. Seeds of AL-34 cultivar were classified in the sieves 22/ 64?, 12/64? x 3/4, 13/64? x 3/4 and 14/64? x 3/4, realizing the following evaluations: germination on humidified paper (with distilate water or with PEG 6000 solutions with water potential of -0.41; -0.81; -1.22 and -1.62MPa), primary root emission at three days, types of seedlings anormalities, seeds viability (tetrazolium test) and dead seeds. Also were realized weigth determination of 100 seeds, cold test without soil, colour test with dye iodine and field emergence. There wasn?t any influence of the shape and size of seeds in the cold test, field emergency, and mechanical damage. The weigth of seeds didn´t affect its performance. It was observed that the seeds of the categories 22/64? (flattned) and 12/64? x 3/4 (smaller among the circular ones) have higher germination percentages than other categories of seeds under normal water conditions. The categories of seeds don?t differ on the germination percentage under condition of water stress, but only in taxes at -0.41MPa, the categories 22/64? and 12/64? x 3/4 present a higher germination rate.