This article presents an analysis of scintillation effects after propagation through atmospheric turbulence. It uses an expansion of the log-amplitude on the Zernike modes in the weak perturbation regime. An analytical evaluation of the error introduced by scintillation on wavefront slope measurements is then derived. For a typical profile corresponding to astronomical conditions, scintillation introduces a wavefront measurement error whose standard deviation is of the order of (lambda) /20 in the visible.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.