ESDU Aero A.06.01.09 gives curves for the variation with freestream Mach number, quarter-chord sweep angle, and section two-dimensional lift-curve slope, of the dihedral or anhedral 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. Three sets of curves are given applying to taper ratios of 0, 0.5 and 1. The curves apply to a gull wing with dihedral from the wing root to some spanwise outboard station. For a wing with dihedral starting at some outboard spanwise station, the contribution of dihedral to the derivative is found from the difference between the contributions for a wing with full-span dihedral (from ESDU Aero A.06.01.03) and for one with dihedral from the root to the station where dihedral starts on the real wing. A similar approach may be applied for multiple dihedral angles. 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.