With 2 tables AbstractLength of the internode basal ring (LIBR) in maize is a morphological character that has been associated with resistance to Mediterranean corn borer (MCB), Sesamia nonagrioides Lef. The present study is the first research to evaluate the usefulness of this trait in breeding programmes. Six maize hybrids, from a complete diallel set of four inbred lines (two resistant and two susceptible to MCB), were evaluated under early and late sowing conditions at three locations in northwestern Spain. General and specific combining ability (GCA and SCA, respectively) for LIBR were estimated, and LIBR correlations with grain yield and other important agronomic traits were evaluated. Hybrid by environment interactions were not significant for LIBR and the sums of squares partitioning indicated a greater GCA effect (95%), suggesting that this trait is stable and shows important additive effects for this set of hybrids. Correlation coefficients not only indicate that selection for increasing LIBR could enhance grain yield and other related plant traits (height and silking) but also an increase in the MCB susceptibility. Based on the limited number genotypes evaluated, LIBR could be modified by selection; however, if LIBR is used as an indirect selection criterion to improve MCB resistance, then some negative effects on yield may be expected.