The aim of this study was to investigate the influence of 50 Hz magnetic or static magnetic fields of 0.5 mT on subsets of human CD4 T cells in terms of cytokine release/content, cell proliferation and intracellular free calcium concentration. CD4 T cells can be divided into different subsets on the basis of surface marker expression, such as CD45, and T cells can be divided into naive (CD45RA ) and memory (CD45RA⁻) cells. In this study, the effects of magnetic fields after 24 and 48 h of cell culture were analyzed. We found that the CD4 CD45RA⁻ T subset were more sensitive after 2 h of exposure. Decreases in the release/content of IFN-γ, in cell proliferation and in intracellular free calcium concentrations were observed in exposed CD4 CD45RA⁻ T cells compared to CD4 CD45RA T cells. The results suggest that exposure to the magnetic fields induces a delay in the response to stimulants and that modifications are rapidly reversible, at least after a short exposure.