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We report the effects of a single electron beam pulse (pulse width, 50 ns full width at half-maximum; electron energy, 25 keV; peak current density in the range 600–2500 A cm-2) on the Ni/Ag system, which was chosen because it shows nearly no mutual solubility in the equilibrium phase diagram. The samples were prepared by vacuum evaporating silver layers 70 and 185 nm thick onto nickel single crystals and were analysed by Rutherford backscattering spectrometry and scanning electron microscopy. Extended solid solubilities were attained. The maximum solubility was determined to be 16 at.% Ag in nickel. At the higher current densities mixing is accompanied by a strong loss of silver in the case of the 70 nm silver layer (up to 50% of the deposited layer). The experimental results are discussed on the basis of heat flow model calculations which use Monte Carlo data for the electron depth-dose function. We also propose a tentative explanation for the observed silver losses based on a boiling instability in very thin superheated films.