ESDU 99020 presents three examples of the application of the constrained multivariate optimisation technique CODAS to minimisation of drag of aerofoil sections at fixed Mach number and lift coefficient by use of either leading- and trailing-edge flap deflections or camber line variations. The aim in each example is to minimise the drag coefficient at a single design point, a Mach number of 0.71, lift coefficient of 0.75, with Reynolds number of 20 million and transition fixed at 5 per cent of chord on both surfaces. The flow calculation method used was BVGK for viscous flow. The initial section used was the RAE 2822 (12.11 per cent maximum thickness/chord ratio with leading-edge radius 0.84 per cent of chord), which was designed to have a pressure distribution with a flat rooftop extending to about 50 per cent of chord at a Mach number of 0.66 and lift coefficient of 0.56. ESDU 99020 is one of a series that illustrate the process of using such optimisation techniques, indicate their advantages and reveal the kinds of problems that can arise. An introduction to the application of constrained multivariate optimisation techniques to the design of aerofoil section shapes is given in ESDU 99019.