By considering the particular case of the 2s21S state of helium, it is shown that in the Hartree–Fock approximation autoionizing states of atoms have square-integrable wave functions and are, therefore, bound states. It follows that autoionization is a correlation effect. The autoionizing states must have non-square-integrable wave functions. The origin of the breakdown of the square integrability is studied with the help of a spectral analysis of the first-order wave function.