A set of diallel crosses involving ten parents was evaluated over two locations to determine the genetic control of protein per cent, oil per cent, seed index, percentage of mature seeds and number of seeds per boll. The analysis of pooled data showed that percentage of mature seeds was controlled by additive (D) and non-additive (H1 and H2) genetic effects. Overdominance was noticed. For seed index the D component measuring additive, and the H2 component measuring dominance, variation were significant. Protein content and oil content were primarily under the control of non-additive (H1 and H2) genetic effects, while for number of seeds per boll the variability was accounted for by dominance (H1) effects only. The development of pure lines through appropriate methods is suggested.