In recent years there has been a dramatic increase in the use of nonprecious alloy and porcelain crowns in clinical dentistry. The alloy in these restorations frequently contains a high percentage (greater than 70%) of nickel. Most cases of metal hypersensitivity are related to nickel, and clinical manifestations of the hypersensitivity are the result of a cellular (T lymphocyte) immune response. In this report, we review the cases of two women who demonstrated significant loss of alveolar bone about nickel-rich nonprecious alloy and porcelain crowns. The loss of alveolar bone occurred within 18 months after placement of the restorations. Both individuals displayed a positive patch test to a nickel preparation. These findings suggest that a Type IV hypersensitivity reaction may have accounted for the rapid loss of alveolar bone. Though the majority of individuals treated with nonprecious alloy and porcelain crowns apparently tolerate these restorations quite well, greater care is urged in case selection.