Abstract: Sixteen different isolates Fusarium graminearum were isolated from various local cultivars of maize collected from different locations in Egypt. The isolates of F. graminearum were screaned for their ability to produce deoxynivalenol (DON) using solid state fermentation on rice medium. Fourteen isolates were DON producer and two isolates were DON non producer. Concentration of DON was estimated by visual comparison with known amounts of DON standard. The mean DON concentrations ranged from 22.3-375.2 μ g/g. DON producing and non producing isolates of F. graminearum were tested for their ability to cause Gibberella ear rot in two susceptible maize cultivars. Harvested maize ears were analyzed for disease severity, grain yield and DON concentration. All the tested isolates were pathogenic, more aggressive isolates produced higher DON concentration which indicate that DON can play a role as virulence factor. The high DON producing isolate of F. graminearum was inoculated to six different maiz cultivars to determine when DON was detectable after inoculation and to estimate DON concentrations in inoculated maize kernels. Deoxynivalenol (DON) was detected in the different maize cultivars 48 h post inoculation (PI) and its accumulation peaked at 120 h and decreased after 240 h(PI). DON concentration in inoculated maize cultivars at 120 h (PI) ranged from 2.75-5.55 ( μ g/g), and differences among the cultivars were significant. Understanding when DON are synthesized in the local cultivars will help how to prevent or delay the biosynthesis of this toxin.