The experiments reported herein were carried out at the Research and Experimental Center of the Faculty of Agriculture at Moshtohor, Benha University, Egypt, during 2009, 2010 and 2011 seasons. The aim of this study was to determine some genetic parameters for grain yield and its components in six populations. Genetic variance in F2 plants, positive heterotic effects and inbreeding depression were significant for all studied traits. Over dominance towards the higher parent was detected for all traits under test. The additive gene effects (a) were significant for No. of kernels row-1, ear weight plant-1 in the three crosses, No. of rows ear-1, grain yield plant-1 and 100-kernel weight in the first and second cross, ear length in the third cross and ear diameter in the second cross. Dominance gene effect (d) was significant for all traits in the three crosses except ear length in the third cross. Additive x additive, additive x dominance and dominance x dominance epistatic types of gene action were significant for most traits. High genetic coefficient of variation for ear diameter, ear weight plant-1 and grain yield plant-1, in the three crosses was detected. High heritability values in broad sense were detected for mot traits. High heritability in narrow sense was detected for ear diameter and ear weight plant-1 in all crosses, No. of kernels row-1 in the third cross and grain yield plant-1 in the first and second cross and 100-kernel weight in the second cross. Genetic advance expressed as the percentage of the mean was moderate to high for all the studied traits.