Ten sunflower (Helianthus annuus L.) lines, five testers, and 50 crosses developed in line x tester fashion were evaluated for general combining ability (GCA) and specific combining ability (SCA) effects in a triplicate randomized complete block design, in Faisalabad, during 2009-2010. Genetic variability among genotypes was assessed for days to flowering, days to maturity, plant height, internodal length, leaf area, number of leaves per plant, head diameter, stem girth, percentage of filled achenes, 100 achene weight, achene yield per plant. A-1, A-7, A-27 and A-39 had significant general combining ability effects for days to flowering, days to maturity, internodal length, leaf area, and achene yield per plant. Among testers, A-26 and HBRS-1 were good general combiners for days to flowering, days to maturity, plant height, leaf area, head diameter, stem girth, percentage of filled achenes, 100-achene weight, and achene yield per plant. Crosses A-165 x A-26, A-41 x A-35, A-1 x G-12, and A-41 x HBPS-1 had significant and positive SCA effects for percentage of filled achenes, 100 achene weight, and achene yield per plant. Four best SCA crosses are recommended to be the best hybrids for cultivation. Non-additive type of gene action was found for all of the plant traits, which is desirable for heterosis breeding and may be exploited in hybrid seed production.