Knowledge of the magnitude of genetic variability, heritability and genetic gains in selection of desirable characters could assist the plant breeder in ascertaining criteria to be used for the breeding programmes. Ten open pollinated maize varieties were evaluated at the Teaching and Research farm, University of Ilorin, Nigeria, during 2005 and 2006 cropping seasons to estimate genetic variability, heritability and genetic advance of grain yield and its component characters. The effect of genotype and genotype by year interaction were significant for ear weight and grain yield, while the effect of year was highly significant (P< 0.01) for all the characters. High magnitude of phenotypic and genotypic coefficient of variations as well as high heritability along with high genetic advance recorded for grain yield, number of grains ear-1, ear weight, plant and ear heights provides evidence that these parameters were under the control of additive gene effects and effective selection could be possible for improvement for these characters. Tze Comp3 C2, Acr 94 Tze Comp5, Tze Comp 4-Dmr Srbc2 and Acr 90 Pool 16-Dt were identified as outstanding genotypes for maize grain yield and should be tested at multilocation for their yield performance.