Sunflower is a major oil seed crop in which genetic variance could be exploited considerably for higher seed yield, oil contents and protein percentage by evolving superior F1 hybrids.The best F1 hybrids however can be obtained by crossing inbred parents with good general and specific combining ability due to higher additive, dominance and complementary epistatic genes. Foremost improvement in sunflower breeding requires the urgency in developing the heterotic hybrids which may achieved by exploiting combining ability and hybrid vigour in F1 hybrids developed from crossing genetically diverse female lines with male restorers. The sunflower F1 hybrids are considered more stable, uniform in plant stand, highly self-fertile, extremely productive in terms of seed yields, oil content, earlier in maturity, resistant to lodging, diseases and insect-pests. The present studies were carried-out at experimental field of Oil Seeds Section Agriculture Research Institute, Tandojam from 2009 to 2011. Six cytoplasmic male sterile female lines viz. ARG-0306,64-A-93, PSF-025, SF-187, ARG-0405 and ARG-0505 and three testers RHP-46, RHP-64 and ARG-0106were crossed in a line x tester mating design, thus 18 cross combinations were developed for evaluation and genetic analysis. The characters studied were; days to 50% flowering, days to 90% maturity, plant height, stem girth, head diameter, number of achenes plant-1, 1000-achene weight, seed yield plant-1, seed yield in kg ha-1, oil content and protein percentage. The analysis of variance revealed significant differences among the parents, F1 hybrids and parents vs. hybrids for phenological, seed yield traits, oil content and protein percentage in F1 and F2 hybrids. The significance of mean squares due to parents vs. hybrids recorded for all the traits studied suggested the scope of heterosis breeding in sunflower, whilst the significant differences for lines x tester interactions indicated the importance of specific combining ability (SCA) of hybrids which suggested the involvement of dominant genes in the expression of studied traits. The significant mean squares due to lines and testers both determine the general combining ability (GCA) revealed the predominance effect of additive genes advocating the traits. Significant genetic variability among the plant traits is particularly valuable because variations in plant traits would allow further improvement in sunflower seed yield and quality traits. The major role of dominant genes was very apparent because the ratio of σ2SCA:σ2GCA was significantly higher and degree of dominance (σ2D/ σ2A)1/2 was also greater than unity. These results indicated the preponderance of dominant gene action suggesting the feasibility of hybrid crop development. General combining ability estimates indicated that CMS lines SF-187, 64-A-93 and ARG-0405 whereasfrom testers RHP-46 were found as the best general combiners for early maturity, seed yield, oil and protein traits, hence these parents may be chosen for hybridization programmes to evolve profitable hybrids or synthetic varieties. Specific combining ability and heterotic effects are very important estimates for determining the suitability of F1 hybrid crop development. The hybrids such as SF-187 x RHP-46, 64-A-93 x RHP-46, PAC-ARG-0405 x PAC-ARG-0106, 64-A-93 x RHP-46 and PSF-025 x RHP-64 which involved parents with high x high and high x low GCA effects, exhibited higher positive SCA and heterotic effects for seed yield, oil content and protein percentage while they expressed negative yet desirable SCA effects for phenological traits and plant height. These results suggested that such hybrids are advantageous for the exploitation of hybrid crop development or selection of transgressive segregants in earlier filial generations. The narrow sense heritability estimates were generally low suggesting greater portion of dominant variances against the additive. Heritability results thus suggested that selection for studied traits may be exercised in later segregating generations while giving the opportunity of recombination to occur between desirable genes. Correlation results generally suggested that head diameter and 1000-achene weight have shown significant positive associations withall seed, oiland protein traits, henceboth the traits may be used as most reliable selection criteria to improve yield, oil andprotein traits in sunflower breeding programmes.