The ratios of the stopping cross sections of deuterium ions in titanium and zirconium deuteride films to those in the pure metals have been determined at incident deuteron energies from 300 keV to 2.0 MeV. These ratios are evaluated from measurements of the yields of deuteron elastic scattering in the deuteride films and in films of the pure metals. Although the absolute stopping cross sections cannot be evaluated from the measurements, use of the Brice yield equation allows the ratios of the cross sections in the deuterides to those in the pure metals to be determined. Significant deviations from Bragg's rule are found and these results are in general agreement with recent measurements at lower deuteron energies (40–200 keV). These measurements represent some of the largest deviations from strict additivity of stopping powers yet observed.