The grain yield of pure stands and equi-proportional mixtures of six cultivars of grain sorghum, Sorghum bicolor (L.) Moench, was studied over two crop population densities and two seasons. There were significant differences in grain yield between seasons, crop population densities and sowing combinations. Over all the treatments a 53% reduction in grain yield was realized in the second season. Doubling crop density from 41142 to 82284 plants ha-1 gave a 35% increase in grain yield. The highest-yielding pure stand was cultivar Dabr 1, and in mixtures was Dabr 1 with cultivar Ariana. Over both seasons and crop population densities, mixtures consistently yielded more than the mean of their components, and seven of these outyielded their more productive pure stands.