Thirteen new yellow maize inbred lines were top crossed to three tester, lines  (Gm. 1002 , Gm. 1004 and Gm. 1021) during summer season of 2006. The resultant  39 top crosses with three single crosses checks i.e. 155, 3084 and 3080 were evaluated for grain yield, days to 50 % silking, resistance to late wilt disease, plant and ear heights traits at Gemmeiza and Nubaria Agricultural Research Stations in 2007 summer season. Mean squares for locations exhibited highly significant differences for all of the studied traits. Variances of crosses and  their partitions ; Lines (L), Testers (T) and L x T interaction were highly significant over locations and their combined data variances for each of crosses, lines and testers by location and Line x Tester x loc. were highly significant in the two locations and combined data . Non-additive genetic variance played an important role in the inheritance of all studied traits , except grain yield, which was affected by additive genetic variance ,while, values of K² S.C.A. x Loc. was higher than values of K² G.C.A. x Loc.  for all of the studied traits. Gm. tester inbred line 1021 found to be the best combinor for grain yield, which manifested better G.C.A. effects and high grain yield average performance followed by Gm. 1002 and Gm. 1004 respectively. Results showed that crossing of Gm. 1021 inbred line tester with the tested fife inbred lines i.e. 409 , 401 , 430 , 425 and 417 significantly out yielded the best check S.C. 155(31.15 ard./fed.) by 3.35 , 2.35 , 2.05 , 1.85 and 1.45 ard./fed. respectively. However there were three tested lines i.e. 406 , 414 and 419 yielded 32.8 , 33.3 and 33.4 ard./fed. respectively with the tester line Gm. 1002 and significantly were better than the best check hybrid. Also there were 3 significantly promising new single cross with tester line Gm. 1004 i.e. Gm. 1004 x 404 , Gm. 1004 x 411 and Gm. 1004 x 417 gave 34.3 , 32.7 and 32.7 ard./fed. respectively.  Therefore these eleven new yellow single crosses might be advanced to another steps for testing and releasing as new yellow single cross hybrids.