ESDU Aero A.06.01.03 gives curves for the variation with freestream Mach number, quarter-chord sweep angle, and section two-dimensional lift-curve slope, of the dihedral contribution to the derivative. The section lift-curve slope may be obtained from ESDU Aero W.01.01.05. The contribution varies linearly with dihedral angle and, provided that the lift coefficient is less than 60 per cent of its stalling value, is independent of lift coefficient. Four sets of curves are given applying to taper ratios of 0, 0.25, 0.5 and 1. The data were derived from lifting-line theory and agree with experimental data to within 10 per cent for fully-attached flow. For non-rigid wings allowance must be made for the additional dihedral due to wing deflection under load and a formula is suggested to extend the use of the data to that case. A worked example illustrates the use of the data.