For design load calculations for wind turbines it is necessary to determine the fatigue loads as well as the extreme loads. An advanced method has been presented previously to incorporate extreme turbulence gusts in wind field simulation, the so-called ‘NewGust’ method. The gust generator works by constraining the random parameters of a stochastic wind field simulator. The present article deals with the verification of the mean shape of extreme gusts. On the basis of a statistical analysis an expression of the mean gust shape is obtained. This theoretical gust shape is compared with the mean gust shape determined from both simulated and measured turbulence. The resemblance is remarkably good, which demonstrates the viability of the NewGust method. Copyright © 1999 John Wiley & Sons, Ltd.