This study was conducted in rice through  a  6x6  diallel set analysis excluding reciprocals involving six rice diverse parents for some root and vegetative traits at the Trial Farm of Rice Research and Training Center, Sakha, Kafr El-Sheikh, Egypt during 2010 and 2011 rice growing  seasons. This investigation aimed to assessment the combining ability and heterosis for root and vegetative traits of some rice genotypes at well watering and water stress conditions. The ordinary analysis of variance engaged highly significant differences among genotypes for all studied root and vegetative traits. In addition, both general and specific combining abilities variances were highly significant for all studied traits at both conditions, demonstrating the importance of additive and non-additive genetic variances in determining the performance of these studied traits. Ratios of GCA/SCA were greater than unity for all studied traits, except root volume and number of tillers/plant at normal condition, as well as root/ shoot ratio at drought stress condition, which were less than unity, representative the importance of additive genetic variance in the inheritance of these traits. The greatest general combiners (GCA effects) were IR 7887 for number of tillers/ plant and days to heading (earliness) at both conditions; IR 7887-176-B-2-B and IR 81025-B-347-3 under normal irrigation, as well as the AZUCENA and IR 7887-176-B-2-B under drought for root volume. This result indicating that these entries could be considered as good general combiners for the improvement of these root and vegetative traits. The greatest cross combinations (SCA effects) were: Sakha101 X IR 81025-B-347-3 at normal irrigation and Giza177 X IR7887-176-B-2-B at drought stress for number of tillers/ plant; IR 7887-176-B-2-B X IR 80508-B-194-1-B under normal irrigation and Giza 177 X IR 7887-176-B-2-B under drought stress for days to heading (earliness); Sakha101 X AZUCENA and Sakha 101 X IR7887-176-B-2-B under both conditions for root volume; Sakha101 X IR 80508-B-194-1-B and Sakha101 X Azucena under both conditions for maximum root length; Giza 177 X Sakha101, IR7887-176-B-2-B X IR81025-B-347-3 and IR80508-B-194-B X IR81025-B-k347-3 under both conditions for plant height (shortness. This recommended that these crosses are useful for improvement these traits. The highest significant heterobeltiosis (H_B.P%) in the desirable direction under drought condition were recorded by: Sakha101 X IR 80508-B-194-1-B for root volume; Sakha101 X IR 80508-B-194-1-B for maximum root length; Sakha101 X IR 81025-B-347 for number of tillers /plant. Higher heritability assessments in broad sense (h _B.S%) were detected for root and vegetative traits, demonstrating that genetic variance played the main part of phenotypic variance.