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.