Abstract: Nature and magnitude of gene action and combining ability effects for some important yield contributing characters viz., plant height, branch number plant-1, capsules plant-1, seeds capsule-1, 1000-seed weight, stick yield plant-1 and seed yield plant-1 in sesame were examined to decide breeding strategies and to identify parents and hybrids for future breeding programme. Seven parents (CST 2002, MT 34, OS-Sel-2, TKG 22, AAUDT 9304-14-4, B 67 and Rama) were crossed in a half diallel mating design. The parents, 21 F1s (without reciprocals) and 21 F2s were grown in summer, 2003, in a randomized block design with three replications in Agricultural Farm, Institute of Agriculture, Visva-Bharati University (23°39′N, 87°42′E). Analysis of combining ability was done following Method-2, Model-I of Griffing. Variances due to General Combining Ability (GCA) and Specific Combining Ability (SCA) for all the traits were highly significant in both F1 and F2 generations indicating importance of both additive and non-additive gene action for the inheritance of all the studied characters in both-generations. OS-Sel-2 appeared as best general combiner for seed yield plant-1 in both generations. GCA and mean performance of the genotypes suggested that the performance per se could be a valid indicator of its ability to transmit the desirable attributes to the progenies. Genetic divergence among the parents played a crucial role to produce crosses with significant SCA-effects on seed yield plant-1. Considering SCA-effects, the cross CST 2002xTKG 22 appeared to be promising. AAUDT 9304-14-4xB67 and OS-Sel-2xAAUDT 9304-14-4 involving parents with high GCA and exhibiting significant and positive SCA for seed yield in F1 could be utilized for the selection of superior genotypes in advance segregating generations.