Corn seeds were treated with high purity oxygen ([O3] = 0 g/m3) and oxygen mixed with ozone ([O3] = 20 g/m3) during 6.8 or 20.5 minutes. Germination tests started immediately or 48 h after treatment. Effects of oxidative treatments on germination were determined by measuring seedlings and roots (>3 and >20 mm) rate at 3, 4 and 5 days of germination test. Results obtained for treated seed samples were higher than for untreated ones. A faster start of germination was observed for treated samples. This early germination start led to a larger number of germinated seeds with longer roots at 4 and 5 days. Nevertheless, too long an ozone treatment seemed to be unfavorable for seed growth, whereas a short one seemed to be most beneficial.