We study the ionization structure of O and WC star winds. The CIII lambda 5696 line fluxes both for homogeneous and for the clumped atmospheres are calculated. The scaled mass - flux relation for clumps in the atmosphere is found. The subordinate line profiles are calculated in the context of the stochastic clumping model of the wind. Using this model it is possible to obtain the mean line profile and to reproduce both amplitude and a common pattern of the line profile variability in the spectra of early-type stars. We present the results of the observational investigations of the small-scale line profile variability in the spectra of O 9.5 star alpha Cam. The wavelet power spectra (WPS) both for the calculated and the observed difference spectra are calculated, The calculated WPS are compared with the ones obtained from the observed spectra. Parameters of the clump ensembles in winds of some Wolf-Rayet stars are estimated.