Genetic studies of plant height were made of 8 wheats and the 28 crosses between them using the diallel method of analysis. The inheritance of plant height in a glasshouse-grown F1 diallel set in which vernalization and photoperiodic responses had been removed, indicated close to complete dominance in its expression. A similar F1 set of crosses in the field environment indicated non-allelic interaction in its expression, attributable mainly to the cultivar Chile 1B generally in its crosses with the other 7 wheats. Its removal gave close to complete average dominance in the inheritance of plant height.In the F2 generation in the field its inheritance was again subject to non-allelic interaction, attributed mainly to Chile 1B which, on removal, gave a situation of average partial dominance in height expression.Standardized deviations of Yr and (Wr + Vr) for plant height for the diallels indicated a resonably close association of tallness with dominance and shortness with recessiveness.Frequency distributions of plant height in the F1 and F2 of two crosses from the diallel confirmed certain findings of the diallel analysis.At least two groups of dominant genes were found to influence plant height expression in the crosses of the diallel ; this number must be regarded as a minimal estimate of the number of genes influencing plant height in wheat.