Abstract: Nature of gene action and combining ability is valuable in determining whether heterosis is fixable or predictable. Thus, to know the inheritance pattern of some morphological traits sixty F1 hybrids along with their parents (3 CMS lines and 20 restorer variety) were evaluated to identify best heterotic combinations. The results indicated that the male lines i.e., IR35454-18-1-1-2R, IET201108 and IR52256-9-2-2-1R were identified good general combiner for grain yield and almost all its major components. The higher magnitude of sca than gca variance, greater values of average degree of dominance and lower predictability ratio was observed in all characters studied suggested significant role of non-additive gene action. Out of 60 crosses, about 30% crosses showed significant and desirable sca effects for grain yield along with its important traits, viz., number of fertile spikelets, number of spikelets per panicle and biological yield. High sca effects was observed in the crosses NMS4AxIR633-76-1R, IR58025AxIR19058-107-1R, IR58025AxIR32419-28-3-1-3-3R, NMS4AxIR35454-18-1-1-2R and NMS4AxIR5226-9-2-2-1R. Manifestation of heterobeltiosis for grain yield was significantly superiority of 43 hybrids ranging from 11.63 to 113.04% and 46 hybrids over standard check (Sarjoo-52) ranging from 10.48 to 71.56%. Most of the crosses which exhibited superiority over better parent or standard variety for grain yield also showed significant heterosis for number of fertile spikelets and number of spikelets per panicle. The best cross combination IR58025AxIR48749-53-2-2-2R, NMS4AxIR633-76-1R, IR58025AxIR54853-43-1-3R, IR58025AxIR19058-107-1R and PMS10AxIR54853-43-1-3R, NMS4AxIR52256-9-2-2-1R, NMS4AxIET9352 and IR58025AxIET201102 having more than 50% heterosis in order of merit grain yield and other yield components as well as significant sca effects for major components were most promising combinations and need to be tested on large scale for commercial exploitation of heterosis.