Combining ability analysis was carried out on diallel crosses of 20 yellow maize varieties in four environments. General combining ability variance (σ2g) was of greater importance than specific combining ability (σ2s) in the inheritance of all traits except grain yield and ear length, where the reverse was true. Interaction components (σ2ge, σ2se) were greater than the respective main components (σ2g, σ2s) for grain yield. The study brought out the prominent role of genotype-environmental interactions. Heritability in the broad sense was very high for all traits except grain yield and grain moisture, and narrow sense heritability was also high for all traits except grain yield and ear length.