Frequency measurements at AT- and BT-cut crystals have been carried out for electrolytic loading of palladium films with H and D from 0.10 M LiOH + H2O (0.10 M LiOD + D2O) solutions. The results at BT-cut crystals have shown that film stressing occurs during the early part of H or D deposition and that this stressing is largely reversible upon removal of hydrogen species. In experiments involving addition of H2O to D2O solutions, it has been found that deposition of H into the palladium film is favored over that of D and that H uptake occurs exclusively at H2O levels above 10%, although these experiments have been carried out at much lower current densities than is typical for these investigations.