The chemical resistance factor DIMBOA, (2.4 dihydroxy­7methoxy-1.4 benzoxazin, 3 one), was determined in ten maize geno­types. Laboratory evaluation of resistance of these types against Ostri­nia nubilalis was recorded. The relationship between DIMBOA and resis­tance degree was estimated showing the following results. There is a positive correlation between DIMBOA absorption (at 266 nm) and larval mortality percentage in 50% of the tested inbred lines. Sixty per cent of the tested lines showd a positive correlation be­tween DIMBOA and per cent larval duration. Fifty per cent of these lines showed a negative correlation between DIMBOA and pupal weight. DIM-BOA correlated with the general rating of laboratory resistance in 60% of the tested maize inbred lines. DIMBOA may play an important role as a chemical resistance fac­tor in 60% of the tested inbred lines (Gm. 9, Gm, 6, Gm22, Gm. 14, Gm. 2 and Sids 34), while (Sids 7, Gm. 13, Gm. 4 and Gm. 31) were not af­fected by DIMBOA content.