An investigation was carried out to assess the combining ability and nature of gene action in respect of grain yield and its attributing traits in 87 single cross hybrids of maize developed by crossing three testers with twenty nine newly developed inbreds from the National Yellow Pool in Line x Tester mating design and grown in RCBD design with two replications during rabi 2008-09. The variance among the lines was highly significant for all the traits, whereas variance among testers was significant for number of kernels per row, 100-grain weight, grain yield per plant, fodder yield and grain yield per hectare. The variance due to line x tester interaction was significant for all the traits except ear length, ear circumference, shelling percent and fodder yield indicating differential response of lines with different testers. The SCA variance was higher than the GCA variance for all the characters indicating the performance of non-additive gene action. YPÄ 4#07-20 among the lines and CI-5 among the testers were identified as good general combiner indicating their ability in transmitting additive genes in the desirable direction to their parents and YP Ä 4#07-20 x CI-5 was identified as good specific combiner. Highly significant sca effect was observed in most of the hybrids for all the characters studied and good specific combiners for different characters involved parents with high x high, high x low, low x high and low x low general combinations.