Information on combining ability and heterotic grouping for maize inbred lines are important to breeding successful hybrids. Nine elite inbred lines were crossed in half diallel mating design to develop 36 crosses in 2021 growing season. These crosses plus one check hybrid were evaluated at Sakha, Sids and Mallawi Agricultural Research Stations using a randomized complete block design with three replications for grain yield/plot in 2022 growing season. The results showed that the general (GCA) and specific (SCA) combining ability effects were important in the inheritance of grain yield/plot. However GCA (additive gene effects) was more important than SCA (non-additive gene effects) in the inheritance of this trait. The desirable inbred lines for GCA effects were Sk5001, Sk5004, Sd41 and Sk13. The correlations between means of crosses with both SCA effects-Griffing's and SCA effects-Yang's were 0.51** and 0.94**, respectively. Hence estimating SCA effects proposed by Yang's is more applicable for breeder, because it was more consistent with means. Placement of inbred lines into groups by four classifications methods showed that, the SCA effects-Griffing method and SCA effects Yang method were corresponding, also these two methods were more similar with HSGCA method than agronomic heterosis method. Comparison of the efficiencies of the four classification methods depending on the percentage of superior high yielding crosses obtained across the total number of inter-heterotic crosses in each classification method, showed that the SCA effects-Griffing, SCA effects-Yang and HSGCA methods were comparable in identifying superior crosses and showed better results than agronomic heterosis method. Seven crosses showed a significant superiority relative to the check. The highest yielding crosses from them were Sd41×Sk13 followed by Sk5001×Sk5004, Sk5004×Sd41 and Sk5001×Sd41. These crosses will be evaluated in an extensive testing in the maize breeding program in Egypt.