The exposure of human peripheral blood mononuclear cells to extremely low frequency pulsed electromagnetic fields (PEMFs) increased both the spontaneous and the PHA- and TPA-induced production of interleukin-1 (IL-1) and IL-6. Our results suggest that cells of the monocytic lineage, which are good producers of both IL-1 and IL-6, can be important cellular targets for PEMFs. Taking into account that these cytokines are among the most pleiotropic ones, these data can help us understand the previous reported effects of PEMFs on the proliferation of human lymphocytes and the effects exerted by such fields on cartilage and bone cells, whose physiological activity is highly dependent on IL-1 and IL-6.