This investigation was conducted at Agriculture Research Station, Sakha, Kafr El-Sheikh, Egypt, during 2017 and 2018 seasons to study combining ability, gene action, heterosis, and degree of dominance for grain yield and its contributing traits in some wide compatibility lines. Eight genotypes included the three lines; O2428-P-7-7, Norti, Gz 5121-5-2 as female parents with five testers Dular, Nekken 1, Giza 178, Gz 5934-7-2-3 and IR 25571-31-1, are used in a line X testers cross. The analysis of variance revealed significant differences among parents, crosses and line x tester interaction for all studied traits except panicle weight in parents. The ratio of K² GCA / K² SCA was more than unity for all studied traits indicated preponderance of additive gene effects in the expression of these traits except panicle weight. Rice varieties; Dular and Nekken 1 can be identified as wide compatible lines. Most of F₁ crosses showed significant values in the heterosis for all studied traits. The crosses Norti X Nekken 1 and Norti X Giza 178 showed the highest values for mean performance and the three types of heterosis for grain yield. In addition, the highest significant positive values of specific combining ability were shown in the four cross combinations O2428-P-7-7 X IR25571-31-1, Gz 5121-5-2 X Gz 5934-7-2-3, Gz 5121-5-2  X Dular and Norti X Giza 178. The results of this study indicate that the parental lines can be used for improvement and utilized in hybrid rice breeding program.