[en] The influence of multiple scattering on the measurement of the ionization probability of inner shells by a coincidence technique has been studied theoretically. For a given foil thickness the coincidence yield is evaluated for every detector angle. Numerical results have been obtained by using multiple scattering theory of Sigmund and Winterbon. Estimates of maximum foil thicknesses are given for which the influence of multiple scattering can be neglected. (Auth.)