We present a re-evaluation of the structure function ratios FHe2/FD2, FC2/FD2 and FCa2/FD2 measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. We also present the ratios FC2/FLi2, FCa2/FCa2 and FCa2/FC2 measured at 90 GeV. The results are based on data already published by NMC; the main difference in the analysis is a correction for the masses of the deuterium targets and an improvement in the radiative corrections. The kinematic range covered is 0.0035 ? x ? 0.65, 0.5 ? Q2 ? 90 GeV2 for the He/D, C/D and Ca/D data and 0.0085 ? x ? 0.6, 0.84 ? Q2 ? 17 GeV2 for the Li/C/Ca ones.