There are several methods of restoring cervical abrasion or erosion lesions, including the use of composite resin, glass-ionomer cement, or a combination of these materials. This paper reports the effectiveness of three different materials and techniques in restoring cervical lesions, using marginal leakage as the means of comparison. Wedge-shaped cervical cavities were prepared so that the gingival cavosurface margin of each cavity involved dentin. Half of the specimens in each group were thermocycled. Differences in marginal leakage were more pronounced at the gingival margin. There was no significant difference between the leakage of thermocycled and nonthermocycled specimens. Microleakage can be expected to be minimal in cavities restored with the "sandwich" technique, in which a glass-ionomer cement liner and composite resin restorative material are placed.