To investigate the effect of different environments on maize resistance to gibberella ear rot, disease symptoms, deoxynivalenol (DON) concentration, and grain yield were measured in three maize (Zea mays L.) inbred lines and five hybrids, from 1994 to1996, at six locations in eastern Canada. At each location, all genotypes were inoculated with a three-isolate macroconidial mix of Fusarium graminearum Schwabe [teleomorph: Gibberella zeae (Schw.) Petch] using a kernel-stab inoculation technique. Results show that year to year variation is more important than variation associated with multiple locations in testing for genotypic resistance to gibberella ear rot, according to disease symptoms and DON content. Severe ear rot and higher DON concentrations among genotypes prevailed in 1994, when environmental conditions during the growing season were more favourable for ear rot development. Regression models indicated that higher ear rot severity and DON concentration were associated with an increase in the total number of days from July to September with relative humidity equal to or greater than 80%. In a favourable environment, moderately severe ear rot symptoms gave up to a 48% yield reduction in susceptible maize hybrids.