The molecular beam epitaxy of yttrium films on BaF2 (111) substrates has been studied. The surface morphology and the crystallinity of the yttrium films were investigated by reflection high energy electron diffraction. The growth of yttrium on BaF2 depends strongly on the surface modification of the substrate. For a substrate temperature of 200 degreesC, epitaxial. films grow in the Stranski-Krastanov mode. However, for a BaF2 substrate temperature of 700 degreesC, which is the optimum growth temperature for the growth of yttrium on CaF2, only polycrystalline films are obtained. By optimizing the growth process, we succeeded growing yttrium films on BaF2 substrates having the same crystallinity as yttrium films grown on CaF2 substrates.