A carefully controlled, 2-year study was undertaken to evaluate the clinical performance of castable glass-ceramic crowns used to restore teeth in the posterior segments. After 2 years of clinical performance, three of the original 101 restorations had failed. Of the remaining 98 crowns, 93 were available for recall; All were rated as excellent for color match, marginal adaptation, and cavosurface marginal discoloration. Postoperative sensitivity occurred in only two of the restored teeth and was noted only at the 6-month recall evaluation. Gingival tissue response was also excellent. The results of this study indicate that this material can be used for the esthetic treatment of posterior teeth that are in need of complete-coverage restoration.