ESDU 90030 considers the flat plate (deflecting in a plane normal to the aerofoil surface) and flap (pivoting about a hinge on the aerofoil surface) types of unvented spoilers with or without porosity on the upper surface of a wing with trailing-edge flaps undeployed. It discusses the flow behaviour with variation of spoiler chordwise position and deflection, and illustrates the effect on wing lift-curve slope and shape. By correlating experimental data drawn from the literature, a method is developed for predicting the lift decrement in two-dimensional flow which is then corrected to three dimensions (by scaling by the wing lift-curve slope predicted using ESDU 70011) and for part-span effects by means of an empirically derived factor. The rolling moment is predicted assuming the lift decrement acts at spoiler mid-span and correcting the moment arm for wing taper and for lift carry-over beyond the physical extent of the spoiler at either end. The method allows for any form of porosity (face perforations, hinge-line gaps, spoiler segmentation or edge castellation) up to 0.25 of the spoiler area. Spoiler locations from 0.4 chord to the trailing-edge are covered for spoiler deflections (defined as height as a fraction of chord where height is measured above the aerofoil surface for the plate type or above the pivot for the flap type) from 0.04 to 0.15 where the lower limit is set by the onset of Reynolds number effects. The experimental data used covered a wide range of straight-tapered wing planforms with aspect ratio 3 and above, taper ratios from 0.4 to 1 and mid-chord sweep up to 30 degrees for Mach numbers up to 0.7. Behaviour is affected by wing angle of attack, and limits of applicability for both minimum and maximum incidence are suggested. Sketches show plots of predictions by the method against experimental results; predictions lie within 0.05 for lift coefficient and within 0.007 for rolling moment coefficient for 75 per cent of the data.