Abstract: Combining ability effects were estimated for maize (Zea mays L.) grain yield and six related agronomic traits in 4 x 4 diallel analysis. Mean squares due to genotypes and specific combining ability effects for all traits except number of ears per plant were highly significant. Mean squares due to general combining ability effects were highly significant for ear height and number of grain rows per ear and significant for plant height and 100-grain weight, while these were non-significant for number of ears per plant, number of grains per row and grain yield per hectare. Variances due to specific combining ability were greater and more important for all characters except number of rows per ear. It indicated the presence of non-additive type of gene action. The inbred line USSR-3135 proved to be the best general combiner for number of rows per ear (0.352), number of grains per row (0.537) and grain yield per unit area (0.343), whereas the inbred line IMAN-I was good general combiner for plant height (0.055), inbred line A-637 was good general combiner for ear height and the inbred line ASE-304 was good combiner for 100-grain weight. A cross USSR-3135 x A-637 showed the best specific combining ability effect (3.253) for grain yield.