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An 8 x 8 diallel cross mating design with the parents and F1s was used to estimate gene action and combining ability for yield and yield characters in sesame (Sesamum indicum L.). The experiment was conducted at the National Semi-Arid Resources Research Institute (NaSARRI), Serere, Uganda during the second season of 2013. The traits involved: days to 50% flowering, days to maturity, height to first branch, height to first capsules, plant height, length of the capsule fruiting zone and yield per plant. The genetic variance of combining ability was separated into general (GCA) and specific (SCA) combining ability variance components. Baker’s ratio, coefficients of genetic determination (CGD) were determined for narrow and broad sense heritabilities. High GCA effects were recorded for days to flowering, height of first capsule and number of branches, branches per plant and capsule length. Desirable SCA effects were recorded for Sesim2//5181 x Renner 1-3-1-1 for reduced height of first branch (-9.48*), Sesim1 x Sesim2 for number of branches per plant (0.901*), capsules on branches (20.75**) and yield per plant (2.42*). High Baker’s ratio was recorded for most of the traits except for yield per plant (0.233). CGDbs was high for most of the traits except for days to maturity (0.064), plant height (0.346), capsules on main stem (0.358) and capsule width (0.286). These results suggested that both additive and non-additive gene actions played a greater role in these traits. Sesim 1 had the highest number of desirable traits scored for GCA effects and could be considered as a parent for crossing to produce desirable progeny. Sesim 1 x Sesim 2, Sesim 1 x Ajimo A1-5 and Sesim2//5181 x SPS1438-1-6-4 recorded positive significant SCA effects for yield per plant and therefore they could be recommended for hybrid seed production. Key words: Baker’s ratio, coefficient of genetic determination, gene effects, yield, yield components, sesame.