A study of how strong electron collisions will influence the profile of the line core is made with in the framework of the impact theory. To this end the time-dependent Schrödinger-equation describing the change of state of the atom during the passage of one perturbing electron is solved numerically down to impact parameters equal to the de Broglie-wavelength 2 . In this range the classical description of the perturbing electrons is assumed to be still valid. In the dipole-only case the solution can be expressed exactly by elementary functions. The line profile clearly shows how important it is to consider the strong collisions. All the different ways of doing this lead to nearly the same results.