The aim of this study was to investigate the differences in several adaptive mechanisms and estimating combining ability for drought tolerance in rice. For this objective, one-set of diallel mating design were made. The selected eight parents; (Sakha 104, Line 1368, Giza 178, Giza 177, IET1444, Sakha 101, Giza 159 and G 46B) and their twenty-eight F1 crosses were grown in a randomized complete blocks design with three replicates. Two adjacent experiments were conducted, the first one was non stress (irrigated every 6-days) and the second one was water stress (irrigated every 9-days). The drought measurements recorded at anthesis stage, in addition, yield and some of its components. Mean squares associated with general and specific combining ability were highly significant for all drought measurements, except total amino acids at normal condition in the combined analysis where the values did not reach the level of significant. High GCA/SCA ratio variance was greater than unity for phenols, total amino acids, total soluble sugars, 1000-kernel weight, no. of grains/panicle and grain yield under both environments as well as their combined analysis, suggesting the importance of additive and additive x additive gene action in the expression of these traits. The parental varieties; Sakha104, IET1444 and Giza159 seems to be good combiners for most drought measurements under both environments as well as their combined analysis. These varieties could be considered as excellent parents in breeding program aimed to release high drought tolerant varieties. The best crosses under both irrigation treatments and the combined analysis were; (Sakha104 x Sakha101), (Sakha104 x G46B), (Giza177 x Sakha101) and (Giza177 x Giza159), where these crosses had highly ^ (Sij) for most drought measurements.