Background: Zinc has significant effects on structural and functional activities of many proteins and enzymes involved in biological activities, especially the regulation of immune-system.Symptoms of zinc toxicity include nausea/vomiting, fever, cough, diarrhea, fatigue, neuropathy, and dehydration. Further signs include growth retardation, altered iron function, anemia, copper deficiency, decreased immune function, decreased HDL (high density lipoprotein), increased LDL (low density lipoprotein), and increased HgbA1C.This study was carried out to examine the invitro effects of different concentrations of zinc on viability and death of T-lymphoid (RAJI) CELL line.Methods: In this study, the CELL line was exposed to different concentrations of zinc (10nanoM to 500microM) followed by incubation (37° C, 5% CO2) at various time points (12 to 72 h). The CELLs were, then, evaluated using trypan blue exclusion dye, MTT assay (mitochondorial thiazol tetrazolium), and light microscopy.Results: The results of this study showed almost different responses to different amounts of zinc in the T CELL line (RAJI). Zinc concentrations below 100mM at different incubation time points had little or no effects on the CELL line compared to the controls. Higher concentrations of zinc viability (>10mM) diminished to 70% at 12 hour and less than 50% at 24 to 72 hours of incubation.Conclusion: It can be concluded that zinc has a dose-dependent cytotoxicity effect on RAJI CELLs.