ESDU 72021 provides a means of estimating the contribution of a straight-tapered swept wing to the rolling moment derivative due to yawing at lift coefficients for which the flow remains fully attached and Mach numbers for which the flow is subsonic over the whole of the wing. Data are also included for slender wings of delta and gothic planform. Contributions arising from the basic planform@ dihedral@ twist and trailing-edge flap deflection are considered. ESDU 72021 is concerned only with attached flow conditions but a bibliography of reports concerning separated flow is included.