Preliminary data suggest that dental amalgam and dental nickel alloys can adversely affect the quantity of T-lymphocytes. Human T-lymphocytes can recognize specific antigens, execute effector functions, and regulate the type and intensity of virtually all cellular and humoral immune responses. Normal immune function depends on a proper quantity, quality, and ratio of T-lymphocyte helper and suppressor subsets. Further research may determine the frequency and magnitude of T-lymphocyte reduction and alteration by dental materials.