Glass-ionomer cement has been advocated for use as a base under composite resin restorations. Forty-nine restorations were studied over a 2-year period to test the efficiency of the glass-ionomer cement-composite resin sandwich technique in Class II cavities. The restorations, all placed by one clinician, were assessed at 6-month intervals for color, anatomic form, marginal adaptation, and surface roughness. Seventeen restorations failed during the follow-up period because of progressive loss of glass-ionomer material. Despite the good performance of the composite resin at the occlusal sum faces, the sandwich technique failed to provide acceptable restorations in this clinical trial.