The microleakage of three glass-ionomer restorative materials, one chemically cured and two light cured, was evaluated. Ten restorations of each material were placed, according to manufacturer's instructions, in Class V cavities in bovine incisors. All cavities were prepared with 90-degree cavosurface margins and were located at the cementoenamel junction. Sectioning of the teeth after thermocycling and immersion in methylene blue dye revealed only occasional slight leakage and no statistically significant difference among the three materials.