The present investigation “Heterosis and combining ability studies for yield and yield component characters in Maize (Zea mays L.)” had been undertaken in maize to carry out the combining ability analysis and to estimate heterosis as well as to understand nature of gene action, correlation and path analysis of yield and yield contributing characters. The material composed of 15 lines were crossed with 3 testers in Line x Tester (L x T) design at Maize Research Centre, Agricultural Research Institute, Rajendranagar, Hyderabad during Rabi, 2010-11. The parents ( 15 lines and 3 testers), 45 F1 crosses along with two standard checks ( DHM 115 and DHM 117) were evaluated during kharif, 2011 at College Farm, College of Agriculture, Rajendranagar, Hyderabad, in a Randomized Block Design with three replications. The data were collected on days to 50 per cent tasseling, days to 50 per cent silking, days to maturity, plant height, ear height, ear length, ear girth, number of kernel rows per ear, number of kernels per row, 100-kernel weight and grain yield per plant. The analysis of variance revealed significant differences among the genotypes for all traits studied. Further, the study of analysis of variance for combining ability revealed the preponderance of non additive gene action for all of the traits favouring for the exploitation of heterosis breeding. In general, hybrids were tall and high yielding, compared to the parents. The levels of heterosis were high in several crosses for important traits like grain yield per plant followed by number of kernel rows per ear, 100-kernel weight, number of kernels per row, ear girth, ear length, ear height and plant height. High general combining ability effects for grain yield per plant and other yield component characters were noticed in the inbred lines 5050, 1234, 3511-2, 3521A-2-3 and testers BML 10, BML 7. These parents had resulted in the production of superior single crosses 5050 x BML 10, 3511-2 x BML 7, 1234 x BML 10, 1234 x BML 13 and 5050 x BML 7 for grain yield per plant. Hence had potential application in the crop improvement programmes. Estimates of heterosis, heterobeltiosis and standard heterosis were variable among crosses in desirable direction and some of them turned out to be best specific crosses. The cross combinations 5050 x BML 10, 3511-2 x BML 7, 1234 x BML 10, 1234 x BML 13 and 5050 x BML 7 for grain yield per plant were found to be superior to the standard check DHM 117. These crosses also exhibited superior mean performances and significant positive sca effects. Character association among grain yield per plant and yield contributing characters exhibited that number of kernels per row, ear girth, ear length, 100-kernel weight, plant height, number of kernel rows per ear and ear height had significant and positive correlations with grain yield. Path coefficient analysis had shown direct positive relationship of number of kernels per row, 100 kernel weight, ear girth, number of kernel rows per ear, ear height, ear length, days to 50% silking and days to maturity with grain yield. The indirect effect of these characters on grain yield influenced more by number of kernels per row and 100 kernel weight. The top five superior cross combinations identified in the present investigation 5050 x BML 10, 3511-2 x BML 7, 1234 x BML 10, 1234 x BML 13 and 5050 x BML 7 based on heterosis and combining ability as for grain yield and yield contributing characters are number of kernels per row, 100-kernel weight, number of kernel rows per ear, ear girth and ear length. These crosses may be further tested before releasing as commercial hybrids.