Two-dimensional, incompressible, spatially developing mixing layer simulations are per formed with two classes of perturbations applied at the inlet boundary: (1) combinations of discrete modes from linear stability theory, and (2) a broad spectrum of modes derived from experimentally measured velocity spectra. The discrete modes from linear theory are obtained by solving the Orr-Sommerfeld equation, and linear stability analysis is used to investigate the effect of Reynolds number on the stability of mixing layers. Two-point spatial velocity and autocorrelations are used to estimate the size and lifetime of the resulting coherent structures and to explore possible feedback effects. It is shown that by forcing with a broad spectrum of modes derived from an experimental energy spectrum, many experimentally observed phenomena can be reproduced by a two-dimensional simulation.