The composition of metallic pigmentations in gingiva and dental roots was determined by means of transmission electron microscopy with energy dispersive x-ray microanalysis. The systemic immune response to the metals found in the oral cavity was evaluated in 10 patients by using a modified lymphocyte proliferation test. Immunological results were compared with a group of five controls without metallic materials and pigmentation. Dense particles of various shapes and sizes, as well as of diverse extracellular and intracellular localization patterns, were detected in the pigmented lamina propria gingivae. Metallic deposits consisted predominantly of silver accompanied by selenium or sulfur or both. Besides, Ag, Au, Cr, Ni, Fe, Hg, Cu, and Ti were identified in dentinal tubules of teeth reconstructed with dental alloys. Nine patients with metallic pigmentations had a positive lymphocyte proliferative response to one or more metals present in their own metal reconstructions. Results of this study thus indicated that dental alloys—by virtue of their corrosion process—might pose a significant risk to immunologically susceptible patients.