The structure of the Cu 3Au(0 0 1) surface has been studied by Ne + scattering spectroscopy under impact collision conditions (ICISS) at room temperature. Scattering of low energy ions (Ne +, 0–3 keV) provides scarce structural information due to the high neutralization probability. Using a Ne ++ beam with energy up to 6 keV and profiting also of the relatively high cross-section for Ne + production in violent collisions with Cu atoms well-defined focusing peaks were detected in ICISS polar scans. The ICISS patterns clearly reflect meaningful structural information, consistent with the 50% Cu–50% Au surface truncation proposed by theoretical investigation and supported by previous ISS works. A comparison of experimental scans with Monte Carlo simulations of ion trajectories, taking into account the Ne–Cu and Ne–Au interaction potentials, thermal disorder, neutralization and reionization processes, is presented and the theoretically predicted rippling between Cu and Au atoms in the first layer is discussed.