Abstract ISO 4354:2009 describes the actions of wind on structures and specifies methods of calculating characteristic values of wind loads for use in designing buildings, towers, chimneys, bridges and other structures, as well as their components and appendages. The loads are suitable for use in conjunction with ISO 2394 and other International Standards concerned with wind loads. In particular, ISO 4354:2009 facilitates the conversion between peak- and mean-wind-speed methodologies and covers the three main storm types, synoptic winds, thunderstorms and tropical cyclones (hurricanes and typhoons). ISO 4354:2009 provides the basic methods from which to determine wind loading analytically through the determination of design pressures or orthogonal along-wind and cross-wind forces and moments for structures of simple shape and wind directionality effects, and through wind tunnel or computational determinations of pressure, forces and moments for structures with complex shapes and wind directionality effects resulting in complex combinations of forces and moments. Two methods of analytical determination of design wind loads are given, one based on a peak velocity and the other on a mean velocity.